m68k: select CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS

All supported CPUs other than the old dragonball and in theory other 68000
derivatives use the include/linux/unaligned/access_ok.h implementation
for accessing unaligned variables, so presumably this works everywhere.

However, m68k never selects CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS,
so none of the other conditionals in the kernel get the optimized
implementation.

Select this based on CPU_HAS_NO_UNALIGNED to make the two settings
always match, and then use the generic version of the header.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>