apns: add "phone" APN for AT&T

  * These "phone" provisioned SIM's don't work with the "pta" APN
  * LTE and MMS do work properly with "phone" APN

Change-Id: Iab7b1f441933be12a7a213d047854dd14b479563
Merge remote-tracking branch 'upstream/jellybean' into jellybean