m68knommu: clean up Pin Assignment definitions for the 54xx ColdFire CPU

The Pin Assignment register definitions for the ColdFire 54xx CPU family are
inconsistently named and defined compared to the other ColdFire part
definitions. Rename them with the same prefix as used on other parts,
MCFGPIO_PAR_, and make their definitions include the MCF_MBAR periphperal
region offset.

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