Fixes the following W=1 kernel build warning:

display/dc/dcn10/dcn10_opp.c:52: warning: Function parameter or member 'oppn10' not described in 'opp1_set_truncation'
display/dc/dcn10/dcn10_opp.c:52: warning: Function parameter or member 'params' not described in 'opp1_set_truncation'
display/dc/dcn10/dcn10_opp.c:52: warning: expecting prototype for set_truncation(). Prototype was for opp1_set_truncation() instead
display/dc/dcn10/dcn10_opp.c:161: warning: Function parameter or member 'oppn10' not described in 'opp1_set_pixel_encoding'
display/dc/dcn10/dcn10_opp.c:161: warning: Function parameter or member 'params' not described in 'opp1_set_pixel_encoding'
display/dc/dcn10/dcn10_opp.c:161: warning: expecting prototype for set_pixel_encoding(). Prototype was for opp1_set_pixel_encoding() instead
display/dc/dcn10/dcn10_opp.c:183: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 *      Set Clamping

Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Harry Wentland <harry.wentland@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>