char: esp.c: fix possible double-unlock

Hitting either of the break statements in the while loop would cause a
double-unlock of info->lock.

[Jiri Slaby suggested simply returning is safe here, rather than a goto]

Noticed by sparse:
drivers/char/esp.c:2042:2: warning: context imbalance in 'rs_wait_until_sent' - unexpected unlock
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/esp.c

@@ -2040,10 +2040,10 @@ static void rs_wait_until_sent(struct tty_struct *tty, int timeout)
 		msleep_interruptible(jiffies_to_msecs(char_time));
 
 		if (signal_pending(current))
-			break;
+			return;
 
 		if (timeout && time_after(jiffies, orig_jiffies + timeout))
-			break;
+			return;
 
 		spin_lock_irqsave(&info->lock, flags);
 		serial_out(info, UART_ESI_CMD1, ESI_NO_COMMAND);