drm/amd/powerplay: fix bug dpm can't work when resume back on Polaris
Need to initialize the values to 0 since they get or'ed with additional
values. If the initialization is missing, on resume, they may end up
with a combination of stale data and new data.
Fixes dpm on resume.
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>