drm/i915/dp: Expose force_dsc_enable through debugfs

Currently we use force_dsc_enable to force DSC from IGT, but
we dont expose this value to userspace through debugfs.
This patch exposes this through the same dsc_fec_support
debugfs node per connector so that we can restore its value
back after the tests are completed.
Suggested-by: Imre Deak <imre.deak@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190405224821.32435-1-manasi.d.navare@intel.com

drivers/gpu/drm/i915/i915_debugfs.c

@@ -4822,6 +4822,8 @@ static int i915_dsc_fec_support_show(struct seq_file *m, void *data)
 			   yesno(crtc_state->dsc_params.compression_enable));
 		seq_printf(m, "DSC_Sink_Support: %s\n",
 			   yesno(drm_dp_sink_supports_dsc(intel_dp->dsc_dpcd)));
+		seq_printf(m, "Force_DSC_Enable: %s\n",
+			   yesno(intel_dp->force_dsc_en));
 		if (!intel_dp_is_edp(intel_dp))
 			seq_printf(m, "FEC_Sink_Support: %s\n",
 				   yesno(drm_dp_sink_supports_fec(intel_dp->fec_capable)));