RDMA/hns: Add bonding event handler

RDMA/hns: Add bonding event handler

Register netdev notifier for two bonding events NETDEV_CHANGEUPPER
and NETDEV_CHANGELOWERSTATE.

In NETDEV_CHANGEUPPER event handler, check some rules about the HW
constraints when trying to link a new slave to the masteri, and
store some bonding information from the notifier. In unlinking case,
simply check the number of the rest slaves to decide whether the
bond is still supported.

In NETDEV_CHANGELOWERSTATE event handler, not much is done. It
simply sets the bond state when the bond is ready, which will be
used later.

Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://patch.msgid.link/20251112093510.3696363-4-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>