RDMA/providers: Simplify query_gid callback of RoCE providers

ib_query_gid() fetches the GID from the software cache maintained in
ib_core for RoCE ports.

Therefore, simplify the provider drivers for RoCE to treat query_gid()
callback as never called for RoCE, and only require non-RoCE devices to
implement it.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>