drm/amd/display: Address kdoc warnings in dcn30_fpu.c

drm/amd/display: Address kdoc warnings in dcn30_fpu.c

Fixes the following gcc with W=1:

display/dc/dml/dcn30/dcn30_fpu.c:677: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 * Finds dummy_latency_index when MCLK switching using firmware based
display/dc/dml/dcn30/dcn30_fpu.c:688: warning: Function parameter or member 'dc' not described in 'dcn30_find_dummy_latency_index_for_fw_based_mclk_switch'
display/dc/dml/dcn30/dcn30_fpu.c:688: warning: Function parameter or member 'context' not described in 'dcn30_find_dummy_latency_index_for_fw_based_mclk_switch'
display/dc/dml/dcn30/dcn30_fpu.c:688: warning: Function parameter or member 'pipes' not described in 'dcn30_find_dummy_latency_index_for_fw_based_mclk_switch'
display/dc/dml/dcn30/dcn30_fpu.c:688: warning: Function parameter or member 'pipe_cnt' not described in 'dcn30_find_dummy_latency_index_for_fw_based_mclk_switch'
display/dc/dml/dcn30/dcn30_fpu.c:688: warning: Function parameter or member 'vlevel' not described in 'dcn30_find_dummy_latency_index_for_fw_based_mclk_switch'

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>