dt-bindings: tc358754: add DT bindings

The patch adds bindings to Toshiba DSI/LVDS bridge TC358764.
Bindings describe power supplies, reset gpio and video interfaces.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Maciej Purski <m.purski@samsung.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180725154644.25412-5-a.hajda@samsung.com