drm/i915: fix CB tuning check for ILK+

CB tuning is needed to handle potential process variations that might
cause clock jitter for certain PLL settings.  However, we were setting
it incorrectly since we were using the wrong M value as a check (M1 when
we needed to use the whole M value).  Fix it up, making my HDMI
attached display a little prettier (used to have occasional dots crawl
across the display).
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NKeith Packard <keithp@keithp.com>

drivers/gpu/drm/i915/intel_display.c

@@ -4994,7 +4994,7 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 	} else if (is_sdvo && is_tv)
 		factor = 20;
 
-	if (clock.m1 < factor * clock.n)
+	if (clock.m < factor * clock.n)
 		fp |= FP_CB_TUNE;
 
 	dpll = 0;