drm/amdgpu: Add missing function parameter 'optc' & 'enable' to kdoc in...

drm/amdgpu: Add missing function parameter 'optc' & 'enable' to kdoc in optc3_set_timing_double_buffer()

Fixes the following gcc with W=1:

drivers/gpu/drm/amd/amdgpu/../display/dc/dcn30/dcn30_optc.c:285: warning: Function parameter or member 'optc' not described in 'optc3_set_timing_double_buffer'
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn30/dcn30_optc.c:285: warning: Function parameter or member 'enable' not described in 'optc3_set_timing_double_buffer'

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>