IB/ipoib: Enable ioctl for to IPoIB rdma netdevs

Adds support for ioctl callback in the RDMA netdevs to allow
supporting functions not handled by the generic interface code.

Signed-off-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Eitan Rabin <rabin@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>