net: net_utils: Move ip_to_string to lib/net_utils.c

The function string_to_ip is already in net_utils, which is
compiled unconditionally, but ip_to_string is currently only
accessible if the legacy network stack is selected. This
commit puts ip_to_string in net_utils.c and removes it from the
legacy network code.

Signed-off-by: Adriano Cordova <adrianox@gmail.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

include/net-common.h

@@ -426,6 +426,16 @@ void string_to_enetaddr(const char *addr, uint8_t *enetaddr);
  */
 struct in_addr string_to_ip(const char *s);
 
+/**
+ * ip_to_string() - Convert a string to ip address
+ *
+ * Implemented in lib/net_utils.c (built unconditionally)
+ *
+ * @x: Input ip to parse
+ * @s: string containing the parsed ip address
+ */
+void ip_to_string(struct in_addr x, char *s);
+
 /* copy a filename (allow for "..." notation, limit length) */
 void copy_filename(char *dst, const char *src, int size);