lib/lzo: Optimize code for CPUs with inefficient unaligned access

Some code paths are only benefical on machines with fast unaligned
loads, so only use these if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
defined.

Signed-off-by: Markus F.X.J. Oberhumer <markus@oberhumer.com>
Signed-off-by: zwliew <zhaoweiliew@gmail.com>