drm/radeon/dpm: implement force performance level for CI

Allows you to force the selected performance level via sysfs.

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

diff --cc drivers/gpu/drm/radeon/ci_dpm.c
Simple merge

diff --cc drivers/gpu/drm/radeon/ppsmc.h
Simple merge

diff --cc drivers/gpu/drm/radeon/radeon_asic.c
Simple merge

diff --cc drivers/gpu/drm/radeon/radeon_asic.h
Simple merge