IB: Report using RoCE IP based gids in port caps

For userspace RoCE UD QPs we need to know the GID format that the
kernel uses, e.g when working over older kernels. For that end, add a
new port capability IB_PORT_IP_BASED_GIDS and report it when query
port is issued.

Signed-off-by: Moni Shoua <monis@mellanox.co.il>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>