The core code now ensures that all driver callbacks that receive an
rdma_ah_attrs will have a sgid_attr's pointer if there is a GRH present.

Drivers can use this pointer instead of calling a query function with
sgid_index. This simplifies the drivers and also avoids races where a
gid_index lookup may return different data if it is changed.
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>