net: dsa: add tag format for MxL862xx switches

net: dsa: add tag format for MxL862xx switches

Add proprietary special tag format for the MaxLinear MXL862xx family of
switches. While using the same Ethertype as MaxLinear's GSW1xx switches,
the actual tag format differs significantly, hence we need a dedicated
tag driver for that.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/c64e6ddb6c93a4fac39f9ab9b2d8bf551a2b118d.1770433307.git.daniel@makrotopia.org
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>