drm/i915: set more FBC chicken bits

Add a couple of missing workaround bits for ILK & SNB.  These disable
clock gating on a couple of units that would otherwise prevent FBC from
working.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 40a407f..6abb15f 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2626,6 +2626,8 @@
 #define DISPLAY_PORT_PLL_BIOS_2         0x46014
 
 #define PCH_DSPCLK_GATE_D	0x42020
+# define DPFCUNIT_CLOCK_GATE_DISABLE		(1 << 9)
+# define DPFCRUNIT_CLOCK_GATE_DISABLE		(1 << 8)
 # define DPFDUNIT_CLOCK_GATE_DISABLE		(1 << 7)
 # define DPARBUNIT_CLOCK_GATE_DISABLE		(1 << 5)