drm/amd/pm: not stop rlc for IMU enabled APUs when suspend

For IMU enabled APUs, after sending the PrepareMp1ForUnload message
to SMU in system_features_control, the RLC registers can't be touched.
The driver to stop the rlc in suspending is no longer required.

Signed-off-by: Tim Huang <Tim.Huang@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>