ARM: imx: use MXxy_IO_P2V macros to setup static mappings

This makes less code rely on the virtual constants.

To further simplify code and reduce the needed boilerplate when
defining the static mappings a new helper macro is defined in
mach/hardware.h.

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