libhydra: Move kernel interface to libcharon

This moves hydra->kernel_interface to charon->kernel.

src/libcharon/network/receiver.c

@@ -20,7 +20,6 @@
 
 #include "receiver.h"
 
-#include <hydra.h>
 #include <daemon.h>
 #include <network/socket.h>
 #include <processing/jobs/job.h>
@@ -451,9 +450,8 @@ static job_requeue_t receive_packets(private_receiver_t *this)
 
 	dst = packet->get_destination(packet);
 	src = packet->get_source(packet);
-	if (!hydra->kernel_interface->all_interfaces_usable(hydra->kernel_interface)
-		&& !hydra->kernel_interface->get_interface(hydra->kernel_interface,
-												   dst, NULL))
+	if (!charon->kernel->all_interfaces_usable(charon->kernel)
+		&& !charon->kernel->get_interface(charon->kernel, dst, NULL))
 	{
 		DBG3(DBG_NET, "received packet from %#H to %#H on ignored interface",
 			 src, dst);