IB/mlx4: Replace mechanism for RoCE GID management

Manage RoCE gid table with logic in IB/core, which is common to all
vendors, and remove the mechanism from the mlx4 IB driver.
Since management of the GID cache may lead to index mismatch with the
hardware GID table, a translation between indexes is required when
modifying a QP or creating an address handle.

Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>