net: dsa: make dsa_tree_change_tag_proto actually unwind the tag proto change

net: dsa: make dsa_tree_change_tag_proto actually unwind the tag proto change

The blamed commit said one thing but did another. It explains that we
should restore the "return err" to the original "goto out_unwind_tagger",
but instead it replaced it with "goto out_unlock".

When DSA_NOTIFIER_TAG_PROTO fails after the first switch of a
multi-switch tree, the switches would end up not using the same tagging
protocol.

Fixes: 29b85e0cc6a1 ("net: dsa: restore error path of dsa_tree_change_tag_proto")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20220303154249.1854436-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>