m68k: init the MMU hardware for the 54xx ColdFire

The 54xx ColdFire CPU family has an internal MMU. Up to now though we
have only supported running on them with the MMU disabled.

Add code to the 54xx ColdFire init sequence to initialize the bootmem
used by the usual MMU m68k code for paging init.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Matt Waddel <mwaddel@yahoo.com>
Acked-by: Kurt Mahan <kmahan@xmission.com>