drm/radeon/kms: add dpm support for rs780/rs880

This adds dpm support for rs780/rs880 asics.  This includes:
- clockgating
- dynamic engine clock scaling
- dynamic voltage scaling

set radeon.dpm=1 to enable it.

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

diff --cc drivers/gpu/drm/radeon/Makefile
Simple merge

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

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

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

diff --cc drivers/gpu/drm/radeon/rs780_dpm.c
Simple merge

diff --cc drivers/gpu/drm/radeon/rs780_dpm.h
Simple merge

diff --cc drivers/gpu/drm/radeon/rs780d.h
Simple merge