drm/radeon/kms/pm: add support for no display power states

The lowest power states often cause display problems, so only enable
them when all displays are off.

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

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

diff --cc drivers/gpu/drm/radeon/r100.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_combios.c
Simple merge

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

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