As the NFC controller has different addresses on imx21 and imx27 there
are two different devices needed if not relying on the overloaded cpp
macro NFC_BASE_ADDR.  So some cpp magic is added to minimize code
duplication.

As obviously these two defines need different names, the name of the old
device is #defined to the new one when building for only one of imx21 or
imx27.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>