bsc: Fix compilation on FreeBSD

FreeBSD uses POSIX netinet/in.h for representing socket addresses
data types.

[Holger removed the #ifdef and changed the order of includes to
have specific ones first and system includes later]

openbsc/include/openbsc/bsc_msc.h

@@ -25,6 +25,8 @@
 #include <osmocom/core/write_queue.h>
 #include <osmocom/core/timer.h>
 
+#include <netinet/in.h>
+
 struct bsc_msc_dest {
 	struct llist_head list;