arm64: dts: qcom: add cec clock for apq8016 board

The adv7533 on this board needs a cec clock. Hook it up in the dtsi
to enable CEC for the HDMI transmitters.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Andy Gross <andy.gross@linaro.org>