dt-bindings: drm: msm: update DisplayPort bindings

Add bindings for force-connected mode for simulation and
non-simulation modes, and add more bindings for AUX bridge driver.

The bindings for AUX bridge driver allows dp-sim driver to pre-define
simulation modes in device tree.

The force-connected bindings allows dp driver to switch between
pre-defined simulation mode and non-simulation mode based on hotplug,
and always report connected state to user.

Change-Id: I3a1a3d0ac67ee9e43a37d93e6d95e876da60cb3d
Signed-off-by: Xiaowen Wu <wxiaowen@codeaurora.org>