audio/msm7x30: Use q5v2_msm_audio_mvs_frame struct

Otherwise a packet size of 640, which 7x30 modem doesn't support,
will be used. 7x30 expects a packet size of 320.

Was changed in AudioHardware::AudioStreamOutDirect::write, but
seems to have been forgotten here.

Related kernel change: http://bit.ly/M7ZqMN