drm/amd/pm: enable ACDC feature

The power limit and clock ragne are different in AC mode and DC mode.
Firmware does the setting after this feature is enabled.

Signed-off-by: Kenneth Feng <kenneth.feng@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>