dt-bindings: display: st,stm32-dsi: Handle data-lanes in DSI port node

Handle 'data-lanes' property of the DSI output endpoint, it is possible
to describe DSI link with 1 or 2 data lanes this way.

Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20220926234501.583115-1-marex@denx.de


Signed-off-by: Rob Herring <robh@kernel.org>