drm/i915/cnl: Add Wa_2201832410

"Clock gating bug in GWL may not clear barrier state when an EOT
is received, causing a hang the next time that barrier is used."

HSDES: 2201832410

Cc: Rafael Antognolli <rafael.antognolli@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180307220912.3681-1-rodrigo.vivi@intel.com