Merge branch 'autoload-dsa-tagging-driver-when-dynamically-changing-protocol'

Merge branch 'autoload-dsa-tagging-driver-when-dynamically-changing-protocol'

Vladimir Oltean says:

====================
Autoload DSA tagging driver when dynamically changing protocol

This patch set solves the issue reported by Michael and Heiko here:
https://lore.kernel.org/lkml/20221027113248.420216-1-michael@walle.cc/
making full use of Michael's suggestion of having two modaliases: one
gets used for loading the tagging protocol when it's the default one
reported by the switch driver, the other gets loaded at user's request,
by name.

  # modinfo tag_ocelot
  filename:       /lib/modules/6.1.0-rc4+/kernel/net/dsa/tag_ocelot.ko
  license:        GPL v2
  alias:          dsa_tag:seville
  alias:          dsa_tag:id-21
  alias:          dsa_tag:ocelot
  alias:          dsa_tag:id-15
  depends:        dsa_core
  intree:         Y
  name:           tag_ocelot
  vermagic:       6.1.0-rc4+ SMP preempt mod_unload modversions aarch64

Tested on NXP LS1028A-RDB with the following device tree addition:

&mscc_felix_port4 {
	dsa-tag-protocol = "ocelot-8021q";
};

&mscc_felix_port5 {
	dsa-tag-protocol = "ocelot-8021q";
};

CONFIG_NET_DSA and everything that depends on it is built as module.
Everything auto-loads, and "cat /sys/class/net/eno2/dsa/tagging" shows
"ocelot-8021q". Traffic works as well. Furthermore, "echo ocelot-8021q"
into the aforementioned sysfs file now auto-loads the driver for it.
====================

Link: https://lore.kernel.org/r/20221115011847.2843127-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>