m68k: don't redefine access functions if we have PCI

Some ColdFire platforms do have real PCI buses, so we should not be
re-defining or otherwise mangling the IO access functions for them.
So when CONFIG_PCI is true use the real io.h support.

Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
Reviewed-by: Angelo Dureghello <angelo@sysam.it>
Tested-by: Angelo Dureghello <angelo@sysam.it>