Since I keep getting confused about this and asking about it,
update the documentation.

In the future, especially when we add more reasons for a link
to be disabled, we should add a per-link 'disable state' bitmap
instead of maintaining all these bitmaps with subset logic, to
indicate each of the different states separately.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240318184907.a5b24595b1a2.I92dd7d177b25df189b842d3bcddb1f2b13b1de13@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>