Avoid compiler warning because of unused variable. (reverted from commit a9c6d59da3)

core/net/ip/uip-nameserver.c

@@ -57,9 +57,7 @@ typedef struct uip_nameserver_record {
 } uip_nameserver_record;
 
 /** \brief Initialization flag */
-#if UIP_NAMESERVER_POOL_SIZE > 1
 static uint8_t initialized = 0;
-#endif
 
 /** \name List and memory block
  * @{