FROMLIST: drm: bridge: analogix/dp: try force hpd after plug in lookup failed

FROMLIST: drm: bridge: analogix/dp: try force hpd after plug in lookup failed

Some edp screen do not have hpd signal, so we can't just return
failed when hpd plug in detect failed.

This is an hardware property, so we need add a devicetree property
"analogix,need-force-hpd" to indicate this sutiation.

(am from https://patchwork.kernel.org/patch/8313081/)

Change-Id: If99d29936aafd996c98568d6e184aee6d9c8bc47
Acked-by: Rob Herring <robh@kernel.org>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>