Merge branch 'mlx4-aux-bus'

Petr Pavlu says:

====================
Convert mlx4 to use auxiliary bus

This series converts the mlx4 drivers to use auxiliary bus, similarly to
how mlx5 was converted [1]. The first 6 patches are preparatory changes,
the remaining 4 are the final conversion.

Initial motivation for this change was to address a problem related to
loading mlx4_en/mlx4_ib by mlx4_core using request_module_nowait(). When
doing such a load in initrd, the operation is asynchronous to any init
control and can get unexpectedly affected/interrupted by an eventual
root switch. Using an auxiliary bus leaves these module loads to udevd
which better integrates with systemd processing. [2]

General benefit is to get rid of custom interface logic and instead use
a common facility available for this task. An obvious risk is that some
new bug is introduced by the conversion.

Leon Romanovsky was kind enough to check for me that the series passes
their verification tests.

Changes since v2 [3]:
* Use 'void *' as the event param of mlx4_dispatch_event().

Changes since v1 [4]:
* Fix a missing definition of the err variable in mlx4_en_add().
* Remove not needed comments about the event type in mlx4_en_event()
  and mlx4_ib_event().

[1] https://lore.kernel.org/netdev/20201101201542.2027568-1-leon@kernel.org/
[2] https://lore.kernel.org/netdev/0a361ac2-c6bd-2b18-4841-b1b991f0635e@suse.com/
[3] https://lore.kernel.org/netdev/20230813145127.10653-1-petr.pavlu@suse.com/
[4] https://lore.kernel.org/netdev/20230804150527.6117-1-petr.pavlu@suse.com/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>