drm/vc4: Check for V3D before binner bo alloc

Check that we have a V3D device registered before attempting to
allocate a binner buffer object.
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190516145544.29051-3-paul.kocialkowski@bootlin.com

drivers/gpu/drm/vc4/vc4_v3d.c

@@ -241,6 +241,9 @@ static int bin_bo_alloc(struct vc4_dev *vc4)
 	int ret = 0;
 	struct list_head list;
 
+	if (!v3d)
+		return -ENODEV;
+
 	/* We may need to try allocating more than once to get a BO
 	 * that doesn't cross 256MB.  Track the ones we've allocated
 	 * that failed so far, so that we can free them when we've got