sys/v4l2/gstv4l2object.c: Reprobe devices again instead of taking a cached list as new devices could've been plugged ...

Original commit message from CVS:
Patch by: Mike Ruprecht <cmaiku at gmail dot com>
* sys/v4l2/gstv4l2object.c: (gst_v4l2_class_probe_devices):
Reprobe devices again instead of taking a cached list as new
devices could've been plugged in. Fixes bug #549062.