irda: unbalanced lock_kernel in irnet_ppp

Add the missing unlock_kernel in one ioctl operation.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/irda/irnet/irnet_ppp.c

@@ -707,6 +707,7 @@ dev_irnet_ioctl(
       if(ap->ppp_open && !put_user(ppp_unit_number(&ap->chan),
 						(int __user *)argp))
         err = 0;
+      unlock_kernel();
       break;
 
       /* All these ioctls can be passed both directly and from ppp_generic,