Fix most of the display documentation compile warnings by
documenting struct mpc_funcs functions in dc/inc/hw/mpc.h file.

Remove the following warnings:
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'read_mpcc_state' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'mpc_init_single_inst' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'get_mpcc_for_dpp_from_secondary' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'get_mpcc_for_dpp' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'wait_for_idle' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'assert_mpcc_idle_before_connect' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'init_mpcc_list_from_hw' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_denorm' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_denorm_clamp' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_output_csc' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_ocsc_default' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_output_gamma' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'power_on_mpc_mem_pwr' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_dwb_mux' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'disable_dwb_mux' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'is_dwb_idle' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_out_rate_control' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_gamut_remap' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'program_1dlut' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'program_shaper' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'acquire_rmu' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'program_3dlut' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'release_rmu' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'get_mpc_out_mux' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_bg_color' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_mpc_mem_lp_mode' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'set_movable_cm_location' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'update_3dlut_fast_load_select' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'get_3dlut_fast_load_status' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'populate_lut' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'program_lut_read_write_control' not described in 'mpc_funcs'
./drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:579: warning: Function parameter or struct member 'program_lut_mode' not described in 'mpc_funcs'

Fixes: b8c1c3a8 ("Documentation/gpu: Add kernel doc entry for MPC")
Closes: https://lore.kernel.org/linux-next/20240130134954.04fcf763@canb.auug.org.au/Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Marcelo Mendes Spessoto Junior <marcelomspessoto@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>