misc: mic/scif: re-take a lock on error path

The caller expects that we take this lock again before returning
otherwise it you get double unlocks and races.

Fixes: ba612aa8b487 ('misc: mic: SCIF memory registration and unregistration')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mic/scif/scif_rma.c

@@ -680,6 +680,7 @@ int scif_unregister_window(struct scif_window *window)
 			}
 		} else {
 			/* Return ENXIO since unregistration is in progress */
+			mutex_lock(&ep->rma_info.rma_lock);
 			return -ENXIO;
 		}
 retry: