drm/sis: missing mutex unlock in error path.

airlied: separated this out from a patch on lkml.
Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/char/drm/sis_mm.c

@@ -134,6 +134,7 @@ static int sis_drm_alloc(struct drm_device *dev, struct drm_file *file_priv,
 		      dev_priv->agp_initialized)) {
 		DRM_ERROR
 		    ("Attempt to allocate from uninitialized memory manager.\n");
+		mutex_unlock(&dev->struct_mutex);
 		return -EINVAL;
 	}