m68k: use asm-generic/unaligned.h

M68k essentially duplicates the content of asm-generic/unaligned.h, with
an exception for non-Coldfire configurations. Coldfire configurations
are apparently able to do unaligned accesses. But in an attempt to clean
up and handle unaligned accesses in the same way we ignore that and use
the common asm-generic/unaligned.h directly instead.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Angelo Dureghello <angelo@kernel-space.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>