only enable count_bit functions when actually needed to fix warning reported by Bernhard Fischer
diff --git a/networking/ifupdown.c b/networking/ifupdown.c
index 6a200bb..ff47e60 100644
--- a/networking/ifupdown.c
+++ b/networking/ifupdown.c
@@ -111,6 +111,8 @@
 static char verbose = 0;
 static char **__myenviron = NULL;
 
+#if ENABLE_FEATURE_IFUPDOWN_IPV4 || ENABLE_FEATURE_IFUPDOWN_IPV6
+
 #ifdef CONFIG_FEATURE_IFUPDOWN_IP
 
 static unsigned int count_bits(unsigned int a)
@@ -135,7 +137,6 @@
 }
 #endif
 
-#if ENABLE_FEATURE_IFUPDOWN_IPV4 || ENABLE_FEATURE_IFUPDOWN_IPV6
 static void addstr(char **buf, size_t *len, size_t *pos, char *str, size_t str_length)
 {
 	if (*pos + str_length >= *len) {