drm/amd/pp: Implement force_clock_level for RV

under manual dpm mode, user can set gfx/mem clock
through sysfs pp_dpm_sclk/mclk on Rv.

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