audio: add alsa plugin to send pcm to audiohal [2/2]

PD#TV-65916

Problem:
app wants to use alsa lib to playback pcm, but
alsa lib doesn't support mix function.

Solution:
add alsa plugin to send pcm to audiohal

Verify:
yocto

Change-Id: Ia3c0e8597b631168bacb53a6e664d67c05bb0151
Signed-off-by: wei.du <wei.du@amlogic.com>
3 files changed
tree: da4473b37b47a0f475fe5992608ab20670b3e994
  1. hal_aplug/
  2. include/
  3. src/
  4. Makefile