There's not much point for calculating the changes for the old
state. Instead just disable all scalers when disabling. It's
probably good enough to just disable the crtc_scaler, but just in
case there's a bug disable all scalers.

This means intel_atomic_setup_scalers is only called in the crtc
check function now, so all the transitional code can be removed.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>