drm/i915: Fix intel_pipe_to_cpu_transcoder for UMS

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

This regression has been introduced in

commit 391f75e
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: stable@vger.kernel.org (for 3.13 only)
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>

drivers/gpu/drm/i915/i915_irq.c

@@ -567,8 +567,7 @@ static u32 i915_get_vblank_counter(struct drm_device *dev, int pipe)
 
 		vbl_start = mode->crtc_vblank_start * mode->crtc_htotal;
 	} else {
-		enum transcoder cpu_transcoder =
-			intel_pipe_to_cpu_transcoder(dev_priv, pipe);
+		enum transcoder cpu_transcoder = (enum transcoder) pipe;
 		u32 htotal;
 
 		htotal = ((I915_READ(HTOTAL(cpu_transcoder)) >> 16) & 0x1fff) + 1;