crypto: keywrap - remove assignment of 0 to cra_alignmask

Since this code is zero-initializing the algorithm struct, the
assignment of 0 to cra_alignmask is redundant.  Remove it to reduce the
number of matches that are found when grepping for cra_alignmask.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>