m68knommu: ColdFire 5271 only has a single FEC controller

The inclusion of multiple FEC ethernet platform devices is based around
the FEC address definitions in the platform headers. The ColdFire m527x
platform is defining 2 FEC modules, but the 5271 SoC only has a single
FEC hardware module. The attempt to probe and init a second FEC module
causes a trap and dump on boot on this platform.

Fix the definitions so that only the 5275 SoC platform (which has 2 FEC
hardware modules) defines the second base address.

Reported-by: ertheb <3rth3bnospam@ethe.fr>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>