dt-bindings: phy: add Amlogic AXG MIPI D-PHY bindings

The Amlogic AXg SoCs embeds a MIPI D-PHY to communicate with DSI
panels, this adds the bindings.

This D-PHY depends on a separate analog PHY.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201116101315.71720-2-narmstrong@baylibre.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>