Update ATT Phone APN to stay updated with ATT protocols
Images of a screenshot from a stock AT&T ROM can be found here: http://goo.gl/nK7iSH | http://goo.gl/F0igf0
Signed-off-by: Jacob Whatley <jacob.whatley91@gmail.com>

Change-Id: I7e7e5fd7097086feb6520ff9ebf48514b3d7e6ec