CRAS: audio_thread - Prepare direction checks for loopback
CRAS: audio_thread - Prepare direction checks for loopback

Prepare some check on the normal input path to support loopback streams
and devices as well.  This will help in merging the loopback and input
paths to share more code.

BUG=chromium:304346
TEST=record audio at different sample rates.

Change-Id: I20031f96fe10968ab170c2c901e94b47f7b33a9b
Signed-off-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/172301

drinkcat/adhd,drinkcat/adhd,drinkcat/adhd,drinkcat/adhd,drinkcat/adhd,drinkcat/adhd