ARM: mx3/mx31_3ds: fix compiler warning without CONFIG_USB_ULPI

This fixes:

	arch/arm/mach-mx3/mach-mx31_3ds.c:249: warning: 'mx31_3ds_host2_init' defined but not used
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx3/mach-mx31_3ds.c

@@ -245,7 +245,7 @@ static int mx31_3ds_usbotg_init(void)
 	return err;
 }
 
-static int mx31_3ds_host2_init(struct platform_device *pdev)
+static int __maybe_unused mx31_3ds_host2_init(struct platform_device *pdev)
 {
 	int err;