v4l2: v4l2_camera_file: Store file description

Create a string that describe the file from the path and file
descriptor. This will be used in log messages to clearly identify which
file an operation is related to.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
3 files changed