dt-bindings: drm/bridge: adv7511: Add regulator bindings

Add the regulator supply properties needed by ADV7511 and ADV7533.

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1484117547-26417-2-git-send-email-architt@codeaurora.org