gpu: drm: amd: display: fix kernel-doc warnings

Fix kernel-doc warnings discovered in AMD gpu display driver.
Fixes these warnings:
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:110: warning:
Function parameter or member 'overlap_only'
not described in 'mpcc_blnd_cfg'.

./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:110: warning:
Function parameter or member 'bottom_gain_mode'
not described in 'mpcc_blnd_cfg'.

./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:110: warning:
Function parameter or member 'background_color_bpc'
not described in 'mpcc_blnd_cfg'.

./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:110:
warning: Function parameter or member 'top_gain'
not described in 'mpcc_blnd_cfg'.

./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:110:
warning: Function parameter or member 'bottom_inside_gain'
not described in 'mpcc_blnd_cfg'.

./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:110:
warning: Function parameter or member 'bottom_outside_gain'
not described in 'mpcc_blnd_cfg'.
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Swarup Laxman Kotiaklapudi <swarupkotikalapudi@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h

@@ -91,6 +91,12 @@ enum mpcc_alpha_blend_mode {
  * @global_gain: used when blend mode considers both pixel alpha and plane
  * alpha value and assumes the global alpha value.
  * @global_alpha: plane alpha value
+ * @overlap_only: whether overlapping of different planes is allowed
+ * @bottom_gain_mode: blend mode for bottom gain setting
+ * @background_color_bpc: background color for bpc
+ * @top_gain: top gain setting
+ * @bottom_inside_gain: blend mode for bottom inside
+ * @bottom_outside_gain:  blend mode for bottom outside
  */
 struct mpcc_blnd_cfg {
 	struct tg_color black_color;	/* background color */