TTY: serial, use atomic_inc_return in ioc4_serial

We want to know the value of the atomic variable in intr_connect after
the increment. But atomic_inc doesn't, per definition, return the
value.  It is just a pure coincidence that ia64 defines atomic_inc as
atomic_inc_return.

So fix this mistake by using atomic_inc_return properly.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/ioc4_serial.c

@@ -975,7 +975,7 @@ intr_connect(struct ioc4_soft *soft, int type,
 	BUG_ON(!((type == IOC4_SIO_INTR_TYPE)
 	       || (type == IOC4_OTHER_INTR_TYPE)));
 
-	i = atomic_inc(&soft-> is_intr_type[type].is_num_intrs) - 1;
+	i = atomic_inc_return(&soft-> is_intr_type[type].is_num_intrs) - 1;
 	BUG_ON(!(i < MAX_IOC4_INTR_ENTS || (printk("i %d\n", i), 0)));
 
 	/* Save off the lower level interrupt handler */