crypto: hash - Fix handling of unaligned buffers

The correct way to calculate the start of the aligned part of an
unaligned buffer is:

  offset = ALIGN(offset, alignmask + 1);

However, crypto_hash_walk_done() has:

  offset += alignmask - 1;
  offset = ALIGN(offset, alignmask + 1);

which actually skips a whole block unless offset % (alignmask + 1) == 1.

This patch fixes the problem.

Signed-off-by: Szilveszter Ördög <slipszi@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>