vendor: apns: Add auth_type explanation

* Since it's unclear what the numbers are, make it easier to add a new
  apn by specifying the possible values in a comment at the top
* Also add missing copyright (verified, first LineageOS commit was
  indeed 2016)

Change-Id: Icaf292fd79a903bcf9ef5a3813f6288cffc468ad
(cherry picked from commit 7aded097379bd76b9167cc7f5784bcb3a9858066)
1 file changed