If the gid_attr argument is NULL then the functions behave identically to
rdma_query_gid. ib_query_gid just calls ib_get_cached_gid, so everything
can be consolidated to one function.

Now that all callers either use rdma_query_gid() or ib_get_cached_gid(),
ib_query_gid() API is removed.
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>