iwinfo: add missing include statement

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41955 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/network/utils/iwinfo/src/iwinfo_nl80211.c

@@ -22,6 +22,7 @@
  * Parts of this code are derived from the Linux iw utility.
  */
 
+#include <limits.h>
 #include "iwinfo_nl80211.h"
 
 #define min(x, y) ((x) < (y)) ? (x) : (y)