net: dsa: rename tagging protocol driver modalias

It's autumn cleanup time, and today's target are modaliases.

Michael says that for users of modinfo, "dsa_tag-20" is not the most
suggestive name, and recommends a change to "dsa_tag-id-20".

Andrew points out that other modaliases have a prefix delimited by
colons, so he recommends "dsa_tag:20" instead of "dsa_tag-20".

To satisfy both proposals, Florian recommends "dsa_tag:id-20".

The modaliases are not stable ABI, and the essential information
(protocol ID) is still conveyed in the new string, which
request_module() must be adapted to form.

Link: 20221027210830.3577793-1-vladimir.oltean@nxp.com
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Suggested-by: Michael Walle <michael@walle.cc>
Suggested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>