m68k: add PCI bus code support for the ColdFire M54xx SoC family

The ColdFire M54xx SoC family have a traditional PCI bus interface.
Add the core support code to access and use this bus on these parts.
This code provides all the config space access functions and IO access
functions. It also carries out the PCI bus initialization and hooks into
the kernel PCI subsystem.

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