drm/i915: Fix intel_pipe_to_cpu_transcoder for UMS

drm/i915: Fix intel_pipe_to_cpu_transcoder for UMS

commit a2d213dd77da4710bcb75f8efe85a32e3db8b39b upstream.

We don't have all the drm_crtc&co hanging around in that case.

This regression has been introduced in

commit 391f75e2bf13f105d9e4a120736ccdd8e3bc638b
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Wed Sep 25 19:55:26 2013 +0300

    drm/i915: Fix pre-CTG vblank counter

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=69521
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>