Allows you to force the selected performance level via sysfs.
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

v2: fix typo noticed by Dan Carpenter
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

set radeon.dpm=1 to enable it.
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>