RDMA/netlink: Fix locking around __ib_get_device_by_index

[ Upstream commit f8978bd95cf92f869f3d9b34c1b699f49253b8c6 ]

Holding locks is mandatory when calling __ib_device_get_by_index,
otherwise there are races during the list iteration with device removal.

Since the locks are static to device.c, __ib_device_get_by_index can
never be called correctly by any user out side the file.

Make the function static and provide a safe function that gets the
correct locks and returns a kref'd pointer. Fix all callers.

Fixes: e5c9469e ("RDMA/netlink: Add nldev device doit implementation")
Fixes: c3f66f7b ("RDMA/netlink: Implement nldev port doit callback")
Fixes: 7d02f605 ("RDMA/netlink: Add nldev port dumpit implementation")
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>