Added empty function fr new interface

ws_management_network_size_set was missing

Author: Mika Tervonen

source/6LoWPAN/ws/ws_empty_functions.c

@@ -53,6 +53,15 @@ int ws_management_regulatory_domain_set(
     return -1;
 }
 
+int ws_management_network_size_set(
+    int8_t interface_id,
+    uint8_t network_size)
+{
+    (void)interface_id;
+    (void)network_size;
+    return -1;
+}
+
 int ws_management_channel_mask_set(
     int8_t interface_id,
     uint32_t channel_mask[8])