crypto: caam - defer aead_set_sh_desc in case of zero authsize

To be able to generate shared descriptors for AEAD, the authentication size
needs to be known. However, there is no imposed order of calling .setkey,
.setauthsize callbacks.

Thus, in case authentication size is not known at .setkey time, defer it
until .setauthsize is called.

The authsize != 0 check was incorrectly removed when converting the driver
to the new AEAD interface.

Cc: <stable@vger.kernel.org> # 4.3+
Fixes: 479bcc7c

 ("crypto: caam - Convert authenc to new AEAD interface")
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>