drm/amd/pm: drop unnecessary wrappers around watermark setting

The convertion to "struct dm_pp_clock_range_for_mcif_wm_set_soc15"
is totally unnecessary and can be dropped.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Tested-by: Changfeng Zhu <Changfeng.Zhu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>