Revert "m7-common: remove tfa amp as its still buggy, sounds are loud enough, needs testing"

This reverts commit c81215064125eeb4c5d57d21bd1ff30737e83ce5.

Change-Id: I094854c6ebd1e6436579418b93709fbb66ff5a3a
Merge "Revert "m7-common: remove tfa amp as its still buggy, sounds are loud enough, needs testing"" into kitkat