drm/i915: Fix gen3 self-refresh watermarks

This regression has been introduced in

commit 4fe8590a921d0b2e36e542dbfa89a8c5993f5a3f
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Wed Sep 4 18:25:22 2013 +0300

    drm/i915: Use adjusted_mode appropriately when computing watermarks

I guess we should renable the enabled local variable into something a
notch more descriptive, but that's something for -next.

The effect on my i945gme netbook is pretty severe amounts of underruns
- usually the very first pixel gets used for the entire screeen.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -1625,7 +1625,7 @@ static void i9xx_update_wm(struct drm_crtc *unused_crtc)
 			&to_intel_crtc(enabled)->config.adjusted_mode;
 		int clock = adjusted_mode->crtc_clock;
 		int htotal = adjusted_mode->htotal;
-		int hdisplay = to_intel_crtc(crtc)->config.pipe_src_w;
+		int hdisplay = to_intel_crtc(enabled)->config.pipe_src_w;
 		int pixel_size = enabled->fb->bits_per_pixel / 8;
 		unsigned long line_time_us;
 		int entries;