CRAS: audio_thread - move first_dev helpers.

They are needed earlier in the file by a later commit

BUG=none
TEST=unittests

Change-Id: I37196bddc22c9fcf63cd6e01f61183b51697cc5a
Signed-off-by: Dylan Reid <dgreid@chromium.org>
CRAS: audio_thread - pre-fill the odev when opening it.

Filling the odev with one cb_threshold of data will prevent the client
from seeing two quick requests when adding the first stream.

BUG=none
TEST=unittest and play audio on Yoshi.

Change-Id: Id98aaaf18164e684ba07185f9ae11e9264a219c0

Conflicts:
	cras/src/server/audio_thread.c
CRAS: util - Add helper to add timespecs.

BUG=none
TEST=none =(

Change-Id: Idf70a1cc038395dca20de385401525b755d9f79f
Signed-off-by: Dylan Reid <dgreid@chromium.org>