m68knommu: make 528x FEC platform addressing consistent

If we make all FEC (ethernet) addressing consistent across all ColdFire
family members then we will be able to remove the duplicated plaform data
and use a single setup for all.

So modify the ColdFire 528x FEC addressing so that:

. FECs are numbered from 0 up
. base addresses are absolute (not relative to MBAR peripheral register)
. use a common name for IRQs used

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