drm/amd/display/dc/dce/dce_opp: Demote non-compliant kernel-doc headers

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:109: warning: Function parameter or member 'opp110' not described in 'set_truncation'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:109: warning: Function parameter or member 'params' not described in 'set_truncation'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:154: warning: Function parameter or member 'opp110' not described in 'dce60_set_truncation'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:154: warning: Function parameter or member 'params' not described in 'dce60_set_truncation'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:204: warning: Function parameter or member 'opp110' not described in 'set_spatial_dither'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:204: warning: Function parameter or member 'params' not described in 'set_spatial_dither'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:308: warning: Function parameter or member 'opp110' not described in 'set_temporal_dither'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:308: warning: Function parameter or member 'params' not described in 'set_temporal_dither'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:370: warning: Function parameter or member 'opp110' not described in 'dce110_opp_set_clamping'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:370: warning: Function parameter or member 'params' not described in 'dce110_opp_set_clamping'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:430: warning: Function parameter or member 'opp110' not described in 'dce60_opp_set_clamping'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:430: warning: Function parameter or member 'params' not described in 'dce60_opp_set_clamping'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:478: warning: Function parameter or member 'opp110' not described in 'set_pixel_encoding'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:478: warning: Function parameter or member 'params' not described in 'set_pixel_encoding'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:514: warning: Function parameter or member 'opp110' not described in 'dce60_set_pixel_encoding'
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_opp.c:514: warning: Function parameter or member 'params' not described in 'dce60_set_pixel_encoding'

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Mauro Rossi <issor.oruam@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_opp.c

@@ -97,7 +97,7 @@ enum {
 
 
 
-/**
+/*
  *	set_truncation
  *	1) set truncation depth: 0 for 18 bpp or 1 for 24 bpp
  *	2) enable truncation
@@ -142,7 +142,7 @@ static void set_truncation(
 }
 
 #if defined(CONFIG_DRM_AMD_DC_SI)
-/**
+/*
  *	dce60_set_truncation
  *	1) set truncation depth: 0 for 18 bpp or 1 for 24 bpp
  *	2) enable truncation
@@ -183,7 +183,7 @@ static void dce60_set_truncation(
 }
 #endif
 
-/**
+/*
  *	set_spatial_dither
  *	1) set spatial dithering mode: pattern of seed
  *	2) set spatial dithering depth: 0 for 18bpp or 1 for 24bpp
@@ -291,7 +291,7 @@ static void set_spatial_dither(
 		FMT_SPATIAL_DITHER_EN, 1);
 }
 
-/**
+/*
  *	SetTemporalDither (Frame Modulation)
  *	1) set temporal dither depth
  *	2) select pattern: from hard-coded pattern or programmable pattern
@@ -355,7 +355,7 @@ static void set_temporal_dither(
 		FMT_TEMPORAL_DITHER_EN, 1);
 }
 
-/**
+/*
  *	Set Clamping
  *	1) Set clamping format based on bpc - 0 for 6bpc (No clamping)
  *		1 for 8 bpc
@@ -415,7 +415,7 @@ void dce110_opp_set_clamping(
 }
 
 #if defined(CONFIG_DRM_AMD_DC_SI)
-/**
+/*
  *	Set Clamping for DCE6 parts
  *	1) Set clamping format based on bpc - 0 for 6bpc (No clamping)
  *		1 for 8 bpc
@@ -465,7 +465,7 @@ static void dce60_opp_set_clamping(
 }
 #endif
 
-/**
+/*
  *	set_pixel_encoding
  *
  *	Set Pixel Encoding
@@ -501,7 +501,7 @@ static void set_pixel_encoding(
 }
 
 #if defined(CONFIG_DRM_AMD_DC_SI)
-/**
+/*
  *	dce60_set_pixel_encoding
  *	DCE6 has no FMT_SUBSAMPLING_{MODE,ORDER} bits in FMT_CONTROL reg
  *	Set Pixel Encoding