drm/amd/pp: Implement update_dpm_settings on Tonga

use SW method to update DPM settings by updating SRAM
directly on Tonga.

Reviewed-by: Alex Deucher <alexdeucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>