m68knommu: fix multi-function pin setup for FEC module on ColdFire 523x

The multi-function pin setup code for the FEC ethernet module is using just
plain wrong. Looks like it was cut-and-pasted from other init code. It has
hard coded register addresses that are incorrect for the 523x, and it is
manipulating bits that don't make sense.

Add proper register definitions for the Pin Assignment registers of the 532x,
and then use them to fix the setup code for the FEC hardware module.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>