ARM: mxc: iomux-v1: Fix build warning

Fix the following warning:

CC      arch/arm/plat-mxc/iomux-v1.o
arch/arm/plat-mxc/iomux-v1.c: In function 'mxc_gpio_setup_multiple_pins':
arch/arm/plat-mxc/iomux-v1.c:160: warning: 'ret' may be used uninitialized in this function
arch/arm/plat-mxc/iomux-v1.c:160: note: 'ret' was declared here

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>