stats: Fix build on FreeBSD

include stdint.h for int64_t and use netinet/in.h and not
netinet/ip.h for getting sockaddr_in and such.
diff --git a/src/stats.c b/src/stats.c
index f979bdc..a072370 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -28,8 +28,9 @@
 #include <stdint.h>
 #include <errno.h>
 #include <stdio.h>
+#include <sys/types.h>
 #include <sys/socket.h>
-#include <netinet/ip.h>
+#include <netinet/in.h>
 #include <arpa/inet.h>
 
 #include <osmocom/core/utils.h>