ARM: mx5/mx53_loco: Fix build warning related to gpio_keys_button structure

Fix the following warning:

CC      arch/arm/mach-mx5/board-mx53_loco.o
arch/arm/mach-mx5/board-mx53_loco.c:203: warning: initialization discards qualifiers from pointer target type
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx5/board-mx53_loco.c

@@ -193,7 +193,7 @@ static iomux_v3_cfg_t mx53_loco_pads[] = {
 	.wakeup		= wake,					\
 }
 
-static const struct gpio_keys_button loco_buttons[] __initconst = {
+static struct gpio_keys_button loco_buttons[] = {
 	GPIO_BUTTON(MX53_LOCO_POWER, KEY_POWER, 1, "power", 0),
 	GPIO_BUTTON(MX53_LOCO_UI1, KEY_VOLUMEUP, 1, "volume-up", 0),
 	GPIO_BUTTON(MX53_LOCO_UI2, KEY_VOLUMEDOWN, 1, "volume-down", 0),