rocket: add a mutex_unlock()

This path needs a mutex_unlock().  This is stuff from the bkl to mutex
transition.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/char/rocket.c

@@ -1244,6 +1244,7 @@ static int set_config(struct tty_struct *tty, struct r_port *info,
 		}
 		info->flags = ((info->flags & ~ROCKET_USR_MASK) | (new_serial.flags & ROCKET_USR_MASK));
 		configure_r_port(tty, info, NULL);
+		mutex_unlock(&info->port.mutex);
 		return 0;
 	}