drm/i915/pvc: Implement recommended caching policy

As per the performance tuning guide, set the HOSTCACHEEN bit to
implement the recommended caching policy on PVC.

Signed-off-by: Wayne Boyer <wayne.boyer@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221130170723.2460014-1-wayne.boyer@intel.com