net: dsa: clean up dsa_user_add_cls_matchall()

net: dsa: clean up dsa_user_add_cls_matchall()

The body is a bit hard to read, hard to extend, and has duplicated
conditions.

Clean up the "if (many conditions) else if (many conditions, some
of them repeated)" pattern by:

- Moving the repeated conditions out
- Replacing the repeated tests for the same variable with a switch/case
- Moving the protocol check inside the dsa_user_add_cls_matchall_mirred()
  function call.

This is pure refactoring, no logic has been changed, though some tests
were reordered. The order does not matter - they are independent things
to be tested for.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20241023135251.1752488-3-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>