nvenc: Use NVENC API-capable devices in a loop by default
Submitted by Kyrylo V. Polezhaiev
Default device ID is now 0. In case we have several NVIDIA video cards, user should manually specify device ID for particular encoding element so he should dive into NVENC API level to find out the number of devices and ID of devices with NVENC support.
In pre-LGPLed version of gst-nvenc new nvh264enc elements just take next (or first, if current one is last) device in a bit ugly way.
Maybe we should set device ID to next (first) device by default?