ARM: mx3: use .init_early to initialize cpu type, reset address and iomuxer

This used to be done in .map_io which is supposed to only setup the
memory mapping.

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