msm7x30: target uses ion

Change-Id: I1c2bb425f034a02ff67184a11d9432b2e63c4c55
msm7x30 use BOARD_USES_LEGACY_ALSA_AUDIO flag.

 * So we can build the audio hal in audio-caf

Change-Id: Ic47c217ef706cda1100fb433572aa83cef7debaa