v2: lock dpm level when update pptable by SW method

use SW method to update DPM settings by updating SRAM
directly on Polaris.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>