drm/i915/gen9: Reintroduce WaEnableYV12BugFixInHalfSliceChicken7

This basically reverts commit 465418c6064c
("drm/i915/gen9: Remove WaEnableYV12BugFixInHalfSliceChicken7")
with small addition - marking it as affecting GLK as well.

It was incorrectly considered fixed in production steppings.

References: HSD#2126385, HSD#2131381, HSDES#1504433555, BSID#0764
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
[Mika: s/KBL/GLK on commit message]
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170512112015.19082-1-arkadiusz.hiler@intel.com

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -851,8 +851,10 @@ static int gen9_init_workarounds(struct intel_engine_cs *engine)
 		 */
 	}
 
+	/* WaEnableYV12BugFixInHalfSliceChicken7:skl,bxt,kbl,glk */
 	/* WaEnableSamplerGPGPUPreemptionSupport:skl,bxt,kbl */
 	WA_SET_BIT_MASKED(GEN9_HALF_SLICE_CHICKEN7,
+			  GEN9_ENABLE_YV12_BUGFIX |
 			  GEN9_ENABLE_GPGPU_PREEMPTION);
 
 	/* Wa4x4STCOptimizationDisable:skl,bxt,kbl,glk */