dt-bindings: display: bridge: Document ITE IT6263 LVDS to HDMI transmitter

commit fe385ed87a3dcef1f000b6df9e4ffd4646800515 from
https://github.com/nxp-imx/linux-imx



This patch adds device tree binding for ITE IT6263 LVDS to HDMI transmitter.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>