crypto: crypto4xx - Fix gcc12 uninitialized warning in crypto4xx_crypt

The compiler gcc 12 warns about the IV buffer being uninitialized
in crypto4xx_crypt.  Silence the warning by using the new gcc 12
access attribute to mark crypto4xx_build_pd.

Also fix the IV buffer length as it has been quadrupled (64 instead
of 16).

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