mm-video-v4l2: create pthread with valid file descriptors

pthread_thread is getting called irrespective of whether we get valid fds
or not. In some cases, we get invalid fds and the FD_SET fails.

Check the fds and create pthread only when the fds are valid.

CRs-Fixed: 1114254
Change-Id: I0cdff7ef9f68b43c8fccd5f7e8c51735cdc22be2
2 files changed