serial: of-serial: fix uninitialized kmalloc variable

The info pointer points to an uninitialized kmalloced space.
If a device doesn't have clk property, then info->clk may
have unpredicated value and cause call trace. So use kzalloc
to make sure it is NULL initialized.
Signed-off-by: NJingchang Lu <jingchang.lu@freescale.com>
Acked-by: Arnd Bergmann <arnd@arndb.de
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/of_serial.c

@@ -158,7 +158,7 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
 	if (of_find_property(ofdev->dev.of_node, "used-by-rtas", NULL))
 		return -EBUSY;
 
-	info = kmalloc(sizeof(*info), GFP_KERNEL);
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (info == NULL)
 		return -ENOMEM;