drm/i915/gvt: Select appropriate mmio list at initialization time

Select appropriate mmio list at initialization time, so we don't need to
do duplicated work at where requires the mmio list.

V2:
  - Add a termination mark of mmio list.

Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/gvt.h

@@ -310,6 +310,8 @@ struct intel_gvt {
 	wait_queue_head_t service_thread_wq;
 	unsigned long service_request;
 
+	struct engine_mmio *engine_mmio_list;
+
 	struct dentry *debugfs_root;
 };