drm/bridge/sii8620: add DVI mode support

If the sink device is in HDMI mode, enable infoframe interrupt in scdt
irq handle function else call start_video function immediately, because
in DVI mode, there is no infoframe interrupt provided.

Rename start_hdmi function to start_video and get rid of the old
start_video function. In start_video, if the sink is DVI and mode is
MHL1 or MHl2, write appropriate values to registers else the path
should remain the same as in HDMI mode.

Signed-off-by: Maciej Purski <m.purski@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1510224822-7732-1-git-send-email-m.purski@samsung.com