[media] of: v4l: Document link-frequencies property in video-interfaces.txt

  array contains only one entry.

- clock-noncontinuous: a boolean property to allow MIPI CSI-2 non-continuous

  clock mode.

- link-frequencies: Allowed data bus frequencies. For MIPI CSI-2, for

  instance, this is the actual frequency of the bus, not bits per clock per

  lane value. An array of 64-bit unsigned integers.

Example