dt-bindings: display: convert sharp,ls043t1le01 to DT Schema

The txt binding specified the property "power-supply".
But the example and the actual implementation in the linux-kernel
uses "avdd-supply".
So the binding is adjusted to use avdd-supply as this seems
to be the correct choice.
There are no DT files in the linux kernel to check.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Werner Johansson <werner.johansson@sonymobile.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200408195109.32692-30-sam@ravnborg.org