Merge branch 'net-dsa-tag_dsa-unify-regular-and-ethertype-dsa-taggers'

Tobias Waldekranz says:

====================
net: dsa: tag_dsa: Unify regular and ethertype DSA taggers

The first patch ports tag_edsa.c's handling of IGMP/MLD traps to
tag_dsa.c. That way, we start from two logically equivalent taggers
that are then merged. The second commit does the heavy lifting of
actually fusing tag_dsa.c and tag_edsa.c. The final one just follows
up with some clean up of existing comments.

v2 -> v3:
  - Add the first patch described above as suggested by Andrew.
  - Better documentation of TO_SNIFFER and FORWARD tags.
  - Spelling.

v1 -> v2:
  - Fixed some grammar and whitespace errors.
  - Removed unnecessary default value in Kconfig.
  - Removed unnecessary #ifdef.
  - Split out comment fixes from functional changes.
  - Fully document enum dsa_code.
====================

Link: https://lore.kernel.org/r/20201114234558.31203-1-tobias@waldekranz.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>