tools: ynl-gen: cleanup user space header includes

Bots started screaming that we're including stdlib.h twice.
While at it move string.h into a common spot and drop stdio.h
which we don't need.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=5464
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=5466
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=5467
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/net/ynl/ynl-gen-c.py

@@ -2323,8 +2323,8 @@ def main():
         headers = ['uapi/' + parsed.uapi_header]
     else:
         cw.p('#include <stdlib.h>')
+        cw.p('#include <string.h>')
         if args.header:
-            cw.p('#include <string.h>')
             cw.p('#include <linux/types.h>')
         else:
             cw.p(f'#include "{parsed.name}-user.h"')
@@ -2339,9 +2339,6 @@ def main():
 
     if args.mode == "user":
         if not args.header:
-            cw.p("#include <stdlib.h>")
-            cw.p("#include <stdio.h>")
-            cw.p("#include <string.h>")
             cw.p("#include <libmnl/libmnl.h>")
             cw.p("#include <linux/genetlink.h>")
             cw.nl()