Make hsync_pin/vsync_pin optional in rpi_dpi_rgb

[FWeinb]

Component name

rpi_dpi_rgb

Link to component documentation on our website

https://esphome.io/components/display/rpi_dpi_rgb

Describe the enhancement

Currently the components requires the declaration of the vsync/hsync_pins but these are not always used. See PandaTouch for example.

Use cases

I would like to get the Panda Touch flashed with esphome to build a little dashboard with it.

Anything else?

PandaTouch pinout

[github-actions[bot]]

🏷️ I've automatically added the component: rpi_dpi_rgb label to help categorize this feature request.