dsp: voice_mhi: use modified mhi sync/put api

MHI APIs have been updated to support LPM. Move to
newer APIs to make use of device LPM.

Change-Id: I68452cdf3f9fc42ca40d472308ed87c0848c7927
Signed-off-by: Aditya Bavanari <abavanar@codeaurora.org>