AudioFlinger: tell HAL the PCM is non-audio

Add a bit to tell the HAL that the PCM data is really encoded audio
wrapped in a data burst.
Otherwise the device may try to play the encoded data directly
which will sound like modulated white noise.

Bug: 22576112
Change-Id: Ib140da96876e849023858fe2510612310501d1ee
Signed-off-by: Phil Burk <philburk@google.com>