m7att: Correct manufacturer, htc to HTC

Change htc for m7att manufacter to HTC to make the string look cleaner
in Android Device Manager and Google Play Store (commonly used by users),
as well as any app that reads ro.product.manufacturer from build.prop.
Also, HTC styles their name in print as being uppercase and generally have
it uppercase in their stock ROMs.

Change-Id: I2c9c341f3c5c7f1a7bb8b145d86e5471a9a9d652
m7att: consolidate device proprietary files under m7-gsm

Change-Id: Ib42bdbd1fa26dd7f5afad5de3bb1e2e31fe3c5a3
m7att: remove GSM APN list

Change-Id: I020ca744c5604e13a237d394cffa667d09a9e4d8