drm/i915: Reject the colorkey ioctls for primary and cursor planes

drm/i915: Reject the colorkey ioctls for primary and cursor planes

The legcy colorkey ioctls are only implemented for sprite planes, so
reject the ioctl for primary/cursor planes. If we want to support
colorkeying with these planes (assuming we have hw support of course)
we should just move ahead with the colorkey property conversion.

Testcase: kms_legacy_colorkey
Cc: Tommi Rantala <tt.rantala@gmail.com>
Cc: stable@vger.kernel.org
Reference: http://mid.gmane.org/CA+ydwtr+bCo7LJ44JFmUkVRx144UDFgOS+aJTfK6KHtvBDVuAw@mail.gmail.com
Reported-and-tested-by: Tommi Rantala <tt.rantala@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>