dt-bindings: drm/panel: simple: Add binding for TFC S9700RTWV43TR-01B

Add bindign for TFC S9700RTWV43TR-01B 7" Three Five Corp 800x480 LCD
panel with resistive touch.

The panel is found on TI AM335x-evm.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/24fea39438decd1e17a9c9afa320d49aca03f60d.1553243203.git.jsarha@ti.com