ARM: imx: export imx_ioremap

The arch_ioremap function on i.MX is now an indirect function pointer.
In order to use it from any loadable module, the pointer itself
has to be exported.

ERROR: "imx_ioremap" [drivers/video/tmiofb.ko] undefined!
ERROR: "imx_ioremap" [drivers/usb/host/sl811-hcd.ko] undefined!
ERROR: "imx_ioremap" [drivers/usb/host/r8a66597-hcd.ko] undefined!
ERROR: "imx_ioremap" [drivers/usb/host/oxu210hp-hcd.ko] undefined!
ERROR: "imx_ioremap" [drivers/usb/gadget/r8a66597-udc.ko] undefined!

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>