m68k: Use generic posix_types.h

Change the m68k architecture to use <asm-generic/posix_types.h>.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1328677745-20121-12-git-send-email-hpa@zytor.com
Cc: Geert Uytterhoeven <geert@linux-m68k.org>