drm/i915/hotplug: Handle CP_IRQ for DP-MST

Handle CP_IRQ in DEVICE_SERVICE_IRQ_VECTOR_ESI0
It requires to call intel_hdcp_handle_cp_irq() in case
of CP_IRQ is triggered by a sink in DP-MST topology.

Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Tested-by: Karthik B S <karthik.b.s@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111081120.28417-4-anshuman.gupta@intel.com