drm/radeon/dpm: add infrastructure to force performance levels

This allows you to force specific power levels within a power
state.  Due to hardware restrictions between generations, the
interface is limited to the following 3 selections:

auto: all levels enabled
low: forced to the lowest power level
high: forced to the highest power level

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
2 files changed