ip: rearrange and prune header files

The recent report of issues with missing limits.h impacting musl
suggested looking at what files are and are not included in ip code.

The standard practice is to put standard headers first, then system,
then local headers. Used iwyu to get suggestions about missing
and extraneous headers.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

ip/iplink.c

@@ -11,17 +11,14 @@
 #include <fcntl.h>
 #include <dlfcn.h>
 #include <errno.h>
-#include <sys/socket.h>
-#include <linux/if.h>
-#include <linux/if_packet.h>
-#include <linux/if_ether.h>
-#include <linux/sockios.h>
-#include <netinet/in.h>
-#include <arpa/inet.h>
 #include <string.h>
-#include <sys/ioctl.h>
-#include <stdbool.h>
-#include <linux/mpls.h>
+#include <strings.h>
+#include <limits.h>
+
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <linux/if.h>
+#include <linux/if_ether.h>
 
 #include "rt_names.h"
 #include "utils.h"

ip/ipnetns.c

@@ -1,21 +1,21 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #define _ATFILE_SOURCE
-#include <sys/file.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/wait.h>
-#include <sys/inotify.h>
-#include <sys/mount.h>
-#include <sys/syscall.h>
+
 #include <stdio.h>
+#include <stdint.h>
 #include <string.h>
-#include <sched.h>
 #include <fcntl.h>
 #include <dirent.h>
 #include <errno.h>
 #include <unistd.h>
 #include <ctype.h>
-#include <linux/limits.h>
+#include <limits.h>
+
+#include <sys/file.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/inotify.h>
+#include <sys/mount.h>
 
 #include <linux/net_namespace.h>
 
@@ -23,7 +23,6 @@
 #include "list.h"
 #include "ip_common.h"
 #include "namespace.h"
-#include "json_print.h"
 
 static int usage(void)
 {