This adds dpm support for sumo asics.  This includes:
- clockgating
- powergating
- dynamic engine clock scaling
- dynamic voltage scaling

set radeon.dpm=1 to enable it.

v2: fix indention
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>