drm/amd/powerplay: disable cg pg task when pp uninitialize.

fix bug on uvd pg enabled, when reboot vm in pass through case,
we need to notify smu power up uvd/vce if they were power down.
otherwise, the vbios post will fail.

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>