Add extended bit-depth capability to audio hal

Extended bit-depth capability is disabled for now,
until mixer paths are fully updated.

Known issue - at least one device reports S24_LE
but operates as S32_LE, so when enabling extended precision,
PCM playback may be quiet.

Change-Id: Id76e6cb86d14be0bec69a6b4b01d780573eff6be
Signed-off-by: Andy Hung <hunga@google.com>