drm/i915/dsi: add ports to intel_dsi to describe the ports being driven

Later on this can include multiple ports (e.g. (1 << PORT_A) | (1 <<
PORT_C)) to describe dual link DSI.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Gaurav K Singh <gaurav.k.singh@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dsi.h

@@ -78,6 +78,9 @@ struct intel_dsi {
 
 	struct intel_connector *attached_connector;
 
+	/* bit mask of ports being driven */
+	u16 ports;
+
 	/* if true, use HS mode, otherwise LP */
 	bool hs;