crypto: mediatek - Fix endianness bugs and sparse warnings

This patch squashes all the sparse warnings in mediatek, some of
which appear to be genuine bugs.  In particular, previously on
BE the keys and IVs all get 32-bit swabbed which can't be right
because they don't get swabbed on LE.  I presume LE is the one
that actually works.

Another funky thing is that the GHASH key gets swabbed on LE.
This makes no sense but I'm presuming someone actually tested
this on LE so I'm preserving the swabbing.  Someone needs to
test this though as it is entirely possible that GCM is the
only thing that worked on BE but not LE.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>