crypto: ccree - use the full crypt length value

In case of AEAD decryption verifcation error we were using the
wrong value to zero out the plaintext buffer leaving the end of
the buffer with the false plaintext.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Fixes: ff27e85a ("crypto: ccree - add AEAD support")
CC: stable@vger.kernel.org # v4.17+
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>