drm/amd/pm: fix uninitialized variable warnings for vangogh_ppt

1. Fix a issue that using uninitialized mask to get the ultimate frequency.
2. Check return of smu_cmn_send_smc_msg_with_param to avoid using
uninitialized variable residency.

Signed-off-by: Tim Huang <Tim.Huang@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>