drm/amd/display: Fix up kdoc formats in dcn32_fpu.c

Fixes the following gcc with W=1:

drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2806: warning: Cannot understand  * *************************************************************************
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2855: warning: Cannot understand  * *************************************************************************
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2900: warning: Function parameter or member 'dc' not described in 'dcn32_assign_fpo_vactive_candidate'
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2900: warning: Function parameter or member 'context' not described in 'dcn32_assign_fpo_vactive_candidate'
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2900: warning: Function parameter or member 'fpo_candidate_stream' not described in 'dcn32_assign_fpo_vactive_candidate'
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2929: warning: Function parameter or member 'dc' not described in 'dcn32_find_vactive_pipe'
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2929: warning: Function parameter or member 'context' not described in 'dcn32_find_vactive_pipe'
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn32/dcn32_fpu.c:2929: warning: Function parameter or member 'vactive_margin_req_us' not described in 'dcn32_find_vactive_pipe'

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