m68k{nommu}: fixups after the header move

swab.h seems to have been missed during the header merge.
Add conditionals similar to byteorder.h and remove the
now unnecessary byteorder_no/mm.h

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>