lt03lte: cleanup and updating

- Add lt03ltetmo as valid variant

Change-Id: I80d5883527cef667eafb7b26717be0ec01546bd4
lt03lte: enable lte by default

Change-Id: Ia65ee5d15c34aa0dc1336b16e73c111c6df7111c
lt03lte: add hardware button overlay

Change-Id: I57bb7c6880b2f4ba5d2b52f9faa1951351915efa