audio_hal: Improve MS12 initial sequence. [2/2]

PD#SWPL-41522

Problem:
In current start up script, Dolby MS12 library
is decrypted first and then audio server launched
in background, which uses the decrypted MS12
library when audio hal initializes.

The decryption command takes too long (~3seconds)
so it blocks other start script and slows down the
whole system boot up time.

Solution:
Make decryption running in background also, and
wait in audio hal initialization if decryption
is in progress.

Verify:
Verified on TM2 AB311 platform.

Change-Id: I6c29eb1d68f1d1c50c1043927063eacdbc2b4d87
Signed-off-by: Tim Yao <tim.yao@amlogic.com>
3 files changed