drivers/char/n_gsm.c: add missing spin_unlock_irqrestore

Author: Julia Lawall <julia@diku.dk>

Add a spin_unlock_irqrestore missing on the error path.  Converting the
return to break leads to the spin_unlock_irqrestore at the end of the
function.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// 
@@
expression E1;
@@

* spin_lock_irqsave(E1,...);
  <+... when != E1
  if (...) {
    ... when != E1
*   return ...;
  }
  ...+>
* spin_unlock_irqrestore(E1,...);
// 

Signed-off-by: Julia Lawall 
Cc: Greg Kroah-Hartman 
Cc: Alan Cox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 

---
 drivers/char/n_gsm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 
diff --git a/drivers/char/n_gsm.c b/drivers/char/n_gsm.c
index 099105e..04ef3ef 100644
--- a/drivers/char/n_gsm.c
+++ b/drivers/char/n_gsm.c
@@ -919,7 +919,7 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
 		else
 			len = gsm_dlci_data_output_framed(gsm, dlci);
 		if (len < 0)
-			return;
+			break;
 		/* DLCI empty - try the next */
 		if (len == 0)
 			i++;