Use BOARD_USES_LEGACY_ALSA_AUDIO flag

Change-Id: Iaff166f0d71c6d9725b964cbf25136c69f2bfa84
see: https://github.com/Evervolv/android_device_htc_msm7x30-common/commit/a61409ce4133a924c51583e1917164ee32e6ceaf