drm: Use crtc_clock in drm_calc_timestamping_constants()

drm_calc_timestamping_constants() computes the pixel/line/frame
durations based on the crtc_ timing values. The corresponding pixel
clock is in mode->crtc_clock, so we need to use that instead of
mode->clock.

This should fix drm_calc_timestamping_constants() for frame packing
stereo modes.

Reviewed-by: mario.kleiner.de@gmail.com
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/drm_irq.c

@@ -451,7 +451,7 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 				     const struct drm_display_mode *mode)
 {
 	s64 linedur_ns = 0, pixeldur_ns = 0, framedur_ns = 0;
-	int dotclock = mode->clock;
+	int dotclock = mode->crtc_clock;
 
 	/* Fields of interlaced scanout modes are only half a frame duration.
 	 * Double the dotclock to get half the frame-/line-/pixelduration.