Add AT&T HSPA+ APN

to get proper hspa+ data speeds the following apn needs to be added for non
lte devices as well

Change-Id: Ie74521590d98e7c9f659546f7649ff0879bee32e
(cherry picked from commit 1229a90cc7ef30a0f588b26f0f5308fd06903dc4)
Conflicts:
	prebuilt/common/etc/apns-conf.xml