arm64: dts: allwinner: add pineh64 model B

This patch adds the model B of the PineH64.
The model B is smaller than the pine64 model A and has no PCIE slot.

The only devicetree difference with the pineH64 model A, is the PHY
regulator and the HDMI connector node.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>