MHL bridge is usually connected to TV via MHL dongle. Currently plugging
HDMI cable to dongle is handled improperly.

Fix it by splitting connecting of a dongle and a HDMI cable. The driver
should now handle unplugging a sink from a dongle and plugging a
different sink with new edid.

Tested on MHL1, MHL2 and MHL3 using various vendors' dongles both in
DVI and 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/1516705996-8928-1-git-send-email-m.purski@samsung.com