[media] adv7842: Disable access to EDID DDC lines before chip power up

In core_init make sure access to EDID DDC lines are disabled
before chip is powered up. Also DISABLE_AUTO_EDID before power up.
The correct setting is applied later when setting the EDID.
Some sources (MAC) kept on reading EDID even when Hotplug was low
and in the short period in core_init before the DDC lines was enabled
read a corrupt EDID.

Signed-off-by: Martin Bugge <marbugge@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>