[SUNSU]: Fix bogus locking in sunsu_change_mouse_baud()

The lock is not held when calling this function, so we
shouldn't drop then reacquire it.

Based upon a report from Jim MacBaine.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/serial/sunsu.c

@@ -518,11 +518,7 @@ static void sunsu_change_mouse_baud(struct uart_sunsu_port *up)
 
 	quot = up->port.uartclk / (16 * new_baud);
 
-	spin_unlock(&up->port.lock);
-
 	sunsu_change_speed(&up->port, up->cflag, 0, quot);
-
-	spin_lock(&up->port.lock);
 }
 
 static void receive_kbd_ms_chars(struct uart_sunsu_port *up, struct pt_regs *regs, int is_break)