drm/i915/cnl: WA FtrEnableFastAnisoL1BankingFix

drm/i915/cnl: WA FtrEnableFastAnisoL1BankingFix

WA to enable HW L1 Banking fix that allows aniso to operate
at full sample rate.

References: HSD#1937670

Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Anuj Phogat <anuj.phogat@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170829230723.20898-1-rodrigo.vivi@intel.com