MIPS: Octeon: Make octeon-md5 driver endian-agnostic

The octeon crypto co-processor expects values to be big endian.
Wrap the data transfers with cpu_to_be64() and be64_to_cpu()
transformations.

This passes for all the MD5 test vectors in crypto/testmgr.h

Signed-off-by: Paul Martin <paul.martin@codethink.co.uk>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9631/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>