avsync-lib: stop popping frames when system time is invalid

Problem:
It is possible that audio paused the wall clock. In this case wall clock
will return -1.

Solution:
frame_expire() stops popping frames if wall clock is invalid.

Verify:
T5d + Roxton + TRC

Change-Id: I60a54bf72d4a9977970d9fe55ced270a1524a041
2 files changed
tree: 208fd974990ea596ab8f028bf2755fb5554f267d
  1. src/
  2. avsync-lib.mk
  3. Config.in
  4. Makefile