Before reading GRH attributes, need to make sure AH contains GRH,
and in addition, initialize GID type.

Fixes: dbf727de ('IB/core: Use GID table in AH creation and dmac resolution')
Signed-off-by: NEran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: NDaniel Jurgens <danielj@mellanox.com>
Reviewed-by: NMark Bloch <markb@mellanox.com>
Signed-off-by: NLeon Romanovsky <leon@kernel.org>
Signed-off-by: NDoug Ledford <dledford@redhat.com>