m68k: Introduce config option CPU_HAS_NO_UNALIGNED

Use CONFIG_CPU_HAS_NO_UNALIGNED instead of open coding CONFIG_M68000 ||
CONFIG_COLDFIRE

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Greg <Ungerer&lt;gerg@uclinux.org>