CRAS: cras_sco - Fix SCO fd checking

Initialize SCO fd as -1 because value 0 is valid.

BUG=b:183594508
TEST=emerge, unittest

Change-Id: I0fc7c6c6f91a2e48ae503fa0167e088baf7f9183
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/2879121
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Hsinyu Chao <hychao@chromium.org>
Commit-Queue: Hsinyu Chao <hychao@chromium.org>
1 file changed