dt-bindings: display: convert sony,acx565akm to DT Schema

dt-bindings: display: convert sony,acx565akm to DT Schema

v2:
  - drop use of spi-slave.yaml (Maxime)
  - add unevaluatedProperties (Maxime)
  - rename node in example to panel (Rob)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200408195109.32692-27-sam@ravnborg.org