drm/i915/icl: Handle hotplug interrupts for DP over TBT

This patch enables hotplug interrupts for DP over TBT output on TC
ports. The TBT interrupts are enabled and handled irrespective of the
actual output type which could be DP Alternate, DP over TBT, native DP
or native HDMI.

Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180616000530.5357-3-paulo.r.zanoni@intel.com