m68k: rework raw access macros for the non-MMU case

The primary and fundamental access macros are really the __raw versions.
So make them the actual implementation for access, and not the read/write
access macros. The read/write macros and functions are built on top of
the raw access (with byte swapping or other actions as required).

This in itself causes no functional change right now. But it will make it
easier to fix and resolve problems with PCI bus access in the future.

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