Introduce a new netlink command to allow rdma event monitoring.
The rdma events supported now are IB device
registration/unregistration and net device attachment/detachment.

Example output of rdma monitor and the commands which trigger
the events:

$ rdma monitor
$ rmmod mlx5_ib
[UNREGISTER]	dev 1 rocep8s0f1
[UNREGISTER]	dev 0 rocep8s0f0

$ modprobe mlx5_ib
[REGISTER]	dev 2 mlx5_0
[NETDEV_ATTACH]	dev 2 mlx5_0 port 1 netdev 4 eth2
[REGISTER]	dev 3 mlx5_1
[NETDEV_ATTACH]	dev 3 mlx5_1 port 1 netdev 5 eth3

$ devlink dev eswitch set pci/0000:08:00.0 mode switchdev
[UNREGISTER]	dev 2 rocep8s0f0
[REGISTER]	dev 4 mlx5_0
[NETDEV_ATTACH]	dev 4 mlx5_0 port 30 netdev 4 eth2

$ echo 4 > /sys/class/net/eth2/device/sriov_numvfs
[NETDEV_ATTACH]	dev 4 rdmap8s0f0 port 2 netdev 7 eth4
[NETDEV_ATTACH]	dev 4 rdmap8s0f0 port 3 netdev 8 eth5
[NETDEV_ATTACH]	dev 4 rdmap8s0f0 port 4 netdev 9 eth6
[NETDEV_ATTACH]	dev 4 rdmap8s0f0 port 5 netdev 10 eth7
[REGISTER]	dev 5 mlx5_0
[NETDEV_ATTACH]	dev 5 mlx5_0 port 1 netdev 11 eth8
[REGISTER]	dev 6 mlx5_0
[NETDEV_ATTACH]	dev 6 mlx5_0 port 1 netdev 12 eth9
[REGISTER]	dev 7 mlx5_0
[NETDEV_ATTACH]	dev 7 mlx5_0 port 1 netdev 13 eth10
[REGISTER]	dev 8 mlx5_0
[NETDEV_ATTACH]	dev 8 mlx5_0 port 1 netdev 14 eth11

$ echo 0 > /sys/class/net/eth2/device/sriov_numvfs
[UNREGISTER]	dev 5 rocep8s0f0v0
[UNREGISTER]	dev 6 rocep8s0f0v1
[UNREGISTER]	dev 7 rocep8s0f0v2
[UNREGISTER]	dev 8 rocep8s0f0v3
[NETDEV_DETACH]	dev 4 rdmap8s0f0 port 2
[NETDEV_DETACH]	dev 4 rdmap8s0f0 port 3
[NETDEV_DETACH]	dev 4 rdmap8s0f0 port 4
[NETDEV_DETACH]	dev 4 rdmap8s0f0 port 5
Signed-off-by: Chiara Meiohas <cmeiohas@nvidia.com>
Signed-off-by: Michael Guralnik <michaelgur@nvidia.com>
Link: https://patch.msgid.link/20240909173025.30422-7-michaelgur@nvidia.comSigned-off-by: Leon Romanovsky <leon@kernel.org>