drm/i915: Enable hotplug retry

Right now we are aware of two cases that needs another hotplug retry:
- Unpowered type-c dongles
- HDMI slow unplug

Both have a complete explanation in the code to schedule another run
of the hotplug handler.

It could have more checks to just trigger the retry in those two
specific cases but why would sink signal a long pulse if there is
no change? Also the drawback of running the hotplug handler again
is really low and that could fix another cases that we are not
aware.

Also retrying for old DP ports(non-DDI) to make it consistent and not
cause CI failures if those systems are connected to chamelium boards
that will be used to simulate the issues reported in here.

v2: Also retrying for old DP ports(non-DDI)(Imre)

v4: Renamed INTEL_HOTPLUG_NOCHANGE to INTEL_HOTPLUG_UNCHANGED to keep
it consistent(Rodrigo)

Tested-by: Timo Aaltonen <tjaalton@ubuntu.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190712005343.24571-2-jose.souza@intel.com