crypto: qat - Ensure ipad and opad are zeroed

The patch ad511e26 (crypto: qat -
Fix incorrect uses of memzero_explicit) broke hashing because the
code was in fact overwriting the qat_auth_state variable.

In fact there is no reason for the variable to exist anyway since
all we are using it for is to store ipad and opad.  So we could
simply create ipad and opad directly and avoid this whole mess.

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