drm/bridge/sii8620: rewrite hdmi start sequence

MHL3 protocol requires registry adjustments depending on chosen video mode.
Necessary information is gathered in mode_fixup callback. In case of HDMI
video modes driver should also send special AVI and MHL3 infoframes.
The patch introduces generic helpers for handling MHL3 infoframes, in
case of appearance of other users of MHL3 infoframes these function can
be moved to common library.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1485935272-17337-21-git-send-email-a.hajda@samsung.com