drm/radeon/kms/pm: track current voltage (v2)

track the current voltage level and avoid setting it
if the requested voltage is already set.

v2: check voltage type before checking current voltage

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

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

diff --cc drivers/gpu/drm/radeon/r600.c
Simple merge

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

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

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

diff --cc drivers/gpu/drm/radeon/rv770.c
Simple merge