Don't check the auth algorithm for GCM.

The upstream OpenSSL changes only set the cipher for GCM since the
authentication is redundant, and changes to OCF will soon remove the
GCM authentication algorithm constants entirely for the same reason.
In addition, ktls_create_session() already validates these fields and
wouldn't pass down an invalid auth_algorithm value to any drivers or
ktls backends.

Reviewed by: hselasky
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D23671