drm/i915/lspcon: Add dp_to_lspcon helper()

We need to get to LSPCON in the next patch, so factor out the helper for
it. While at it also remove the redundant GEN9 check.

Cc: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479755707-29596-3-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/intel_drv.h

@@ -1089,6 +1089,12 @@ dp_to_dig_port(struct intel_dp *intel_dp)
 	return container_of(intel_dp, struct intel_digital_port, dp);
 }
 
+static inline struct intel_lspcon *
+dp_to_lspcon(struct intel_dp *intel_dp)
+{
+	return &dp_to_dig_port(intel_dp)->lspcon;
+}
+
 static inline struct intel_digital_port *
 hdmi_to_dig_port(struct intel_hdmi *intel_hdmi)
 {