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: 53448aed

 ("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>