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

 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:547: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:603: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:629: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1006: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1155: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1608: warning: expecting prototype for Populates single SMC GFXSCLK structure using the provided engine clock(). Prototype was for vega10_populate_single_gfx_level() instead
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1663: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1713: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1862: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:2546: warning: expecting prototype for Initializes the SMC table and uploads it(). Prototype was for vega10_init_smc_table() instead
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:2922: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst

Cc: Evan Quan <evan.quan@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: 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>