video: add header file for Mobile High-Definition Link (MHL) interface

This header adds definitions specific to MHL protocol.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1475823762-16237-2-git-send-email-a.hajda@samsung.com