On certain VIA chipsets AES-CBC requires the input/output to be
a multiple of 64 bytes.  We had a workaround for this but it was
buggy as it sent the whole input for processing when it is meant
to only send the initial number of blocks which makes the rest
a multiple of 64 bytes.

As expected this causes memory corruption whenever the workaround
kicks in.
Reported-by: NPhil Sutter <phil@nwl.cc>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>