drm/amd/display: Move DIO documentation to the right place

When building the kernel-doc, it complains with the below warning:

./drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.h:1: warning: no structured comments found
./drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.h:1: warning: no structured comments found

This warning was caused by the wrong use of the ':export:' and the lack
of function documentation in the file pointed under the ':internal:'.
This commit addresses those issues by relocating the overview
documentation to the correct C file, removing the ':export:' options,
and adding two simple kernel-doc to ensure that ':internal:' does not
have any warning.

Cc: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/dri-devel/20240715085918.68f5ecc9@canb.auug.org.au/Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Documentation/gpu/amdgpu/display/dcn-blocks.rst

@@ -68,11 +68,8 @@ OPP
 DIO
 ---
 
-.. kernel-doc:: drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.h
+.. kernel-doc:: drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.c
    :doc: overview
 
-.. kernel-doc:: drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.h
-   :export:
-
-.. kernel-doc:: drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.h
+.. kernel-doc:: drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.c
    :internal:

drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.c

@@ -26,6 +26,16 @@
 #include "core_types.h"
 #include "link_enc_cfg.h"
 
+/**
+ * DOC: overview
+ *
+ * Display Input Output (DIO), is the display input and output unit in DCN. It
+ * includes output encoders to support different display output, like
+ * DisplayPort, HDMI, DVI interface, and others. It also includes the control
+ * and status channels for these interfaces.
+ */
+
+
 void set_dio_throttled_vcp_size(struct pipe_ctx *pipe_ctx,
 		struct fixed31_32 throttled_vcp_size)
 {
@@ -254,12 +264,31 @@ static const struct link_hwss dio_link_hwss = {
 	},
 };
 
+/**
+ * can_use_dio_link_hwss - Check if the link_hwss is accessible
+ *
+ * @link: Reference a link struct containing one or more sinks and the
+ *	  connective status.
+ * @link_res: Mappable hardware resource used to enable a link.
+ *
+ * Returns:
+ * Return true if the link encoder is accessible from link.
+ */
 bool can_use_dio_link_hwss(const struct dc_link *link,
 		const struct link_resource *link_res)
 {
 	return link->link_enc != NULL;
 }
 
+/**
+ * get_dio_link_hwss - Return link_hwss reference
+ *
+ * This function behaves like a get function to return the link_hwss populated
+ * in the link_hwss_dio.c file.
+ *
+ * Returns:
+ * Return the reference to the filled struct of link_hwss.
+ */
 const struct link_hwss *get_dio_link_hwss(void)
 {
 	return &dio_link_hwss;

drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.h

@@ -23,15 +23,6 @@
  *
  */
 
-/**
- * DOC: overview
- *
- * Display Input Output (DIO), is the display input and output unit in DCN. It
- * includes output encoders to support different display output, like
- * DisplayPort, HDMI, DVI interface, and others. It also includes the control
- * and status channels for these interfaces.
- */
-
 #ifndef __LINK_HWSS_DIO_H__
 #define __LINK_HWSS_DIO_H__