USB: ftdi_sio: unlock_kernel() on error in set_serial_info()

There was one error path where unlock_kernel() wasn't called.

This was found with a code checker (http://repo.or.cz/w/smatch.git/)
Compile tested only, sorry.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 64b8429..f92f4d7 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1065,8 +1065,10 @@
 
 	if (!capable(CAP_SYS_ADMIN)) {
 		if (((new_serial.flags & ~ASYNC_USR_MASK) !=
-		     (priv->flags & ~ASYNC_USR_MASK)))
+		     (priv->flags & ~ASYNC_USR_MASK))) {
+			unlock_kernel();
 			return -EPERM;
+		}
 		priv->flags = ((priv->flags & ~ASYNC_USR_MASK) |
 			       (new_serial.flags & ASYNC_USR_MASK));
 		priv->custom_divisor = new_serial.custom_divisor;