drm/i915/gen9: Reintroduce WaEnableYV12BugFixInHalfSliceChicken7

This basically reverts commit 465418c6
("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