socket: add osmo_sockaddr_cmp()

Compare two osmo_sockaddr.

Change-Id: I2d12ebae2710ffd17cf071e6ada0804e73f87dd6
diff --git a/include/osmocom/core/socket.h b/include/osmocom/core/socket.h
index 4441449..e417f42 100644
--- a/include/osmocom/core/socket.h
+++ b/include/osmocom/core/socket.h
@@ -113,5 +113,7 @@
 
 int osmo_sock_local_ip(char *local_ip, const char *remote_ip);
 
+int osmo_sockaddr_cmp(struct osmo_sockaddr *a, struct osmo_sockaddr *b);
+
 #endif /* (!EMBEDDED) */
 /*! @} */