ARM: imx: ehci: use void __iomem * to hold i/o addresses

This fixes:

	arch/arm/plat-mxc/ehci.c: In function 'mxc_initialize_usb_hw':
	arch/arm/plat-mxc/ehci.c:260: warning: assignment makes integer from pointer without a cast
	arch/arm/plat-mxc/ehci.c:263: warning: assignment makes integer from pointer without a cast
	arch/arm/plat-mxc/ehci.c:270: warning: assignment makes integer from pointer without a cast

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>