drm: port over use_vmalloc code from git hashtab

Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/drm_hashtab.h b/drivers/char/drm/drm_hashtab.h
index 40afec0..613091c 100644
--- a/drivers/char/drm/drm_hashtab.h
+++ b/drivers/char/drm/drm_hashtab.h
@@ -47,6 +47,7 @@
 	unsigned int order;
 	unsigned int fill;
 	struct hlist_head *table;
+	int use_vmalloc;
 } drm_open_hash_t;