drm/i915: Removed orphaned prototype intel_dp_handle_hpd_irq()

The function was removed in:

  commit 0e32b39c
  Author: Dave Airlie <airlied@redhat.com>
  Date:   Fri May 2 14:02:48 2014 +1000

      drm/i915: add DP 1.2 MST support (v0.7)
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_drv.h

@@ -992,7 +992,6 @@ void intel_edp_psr_flush(struct drm_device *dev,
 			 unsigned frontbuffer_bits);
 void intel_edp_psr_init(struct drm_device *dev);
 
-int intel_dp_handle_hpd_irq(struct intel_digital_port *digport, bool long_hpd);
 void intel_dp_add_properties(struct intel_dp *intel_dp, struct drm_connector *connector);
 void intel_dp_mst_suspend(struct drm_device *dev);
 void intel_dp_mst_resume(struct drm_device *dev);