drm/i915/ehl: Don't forget to set TC long detect function

Since EHL's MCC PCH reuses one of the TC pins we need to supply a TC
long detect function when handling the interrupts.

Fixes: 53448ae ("drm/i915/ehl: Port C's hotplug interrupt is associated with TC1 bits")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191015161131.21239-1-matthew.d.roper@intel.com
Reviewed-by: Vivek Kasireddy <vivek.kasireddy@intel.com>

drivers/gpu/drm/i915/i915_irq.c

@@ -2251,6 +2251,7 @@ static void icp_irq_handler(struct drm_i915_private *dev_priv, u32 pch_iir)
 	} else if (HAS_PCH_MCC(dev_priv)) {
 		ddi_hotplug_trigger = pch_iir & SDE_DDI_MASK_ICP;
 		tc_hotplug_trigger = pch_iir & SDE_TC_HOTPLUG_ICP(PORT_TC1);
+		tc_port_hotplug_long_detect = icp_tc_port_hotplug_long_detect;
 		pins = hpd_icp;
 	} else {
 		ddi_hotplug_trigger = pch_iir & SDE_DDI_MASK_ICP;