missing: split network related entries

Also adds comments which kernel version added the entries.

Closes #10553.

src/network/netdev/vxcan.c

@@ -1,7 +1,11 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
-#include "netdev/vxcan.h"
+#if HAVE_LINUX_CAN_VXCAN_H
+#include <linux/can/vxcan.h>
+#endif
+
 #include "missing.h"
+#include "netdev/vxcan.h"
 
 static int netdev_vxcan_fill_message_create(NetDev *netdev, Link *link, sd_netlink_message *m) {
         VxCan *v;

src/network/netdev/vxcan.h

@@ -3,10 +3,6 @@
 
 typedef struct VxCan VxCan;
 
-#if HAVE_VXCAN_INFO_PEER
-#include <linux/can/vxcan.h>
-#endif
-
 #include "netdev/netdev.h"
 
 struct VxCan {