Make CONFIG_SND_SOC_TPA6165A2 a bool rather than a tristate

This conditionally reverts Moto commit 744cce122f9ca2a03e69b0df4f24ba43ea8e7f37
Allowing us to select this codec for ghost/obake builds only and
not interfere with vanquish builds.

Change-Id: I6900b87a7cd86888237c2fe8e21b6b3d6867650e