Unix domain: More fixed to build without Ethernet or Slip

arch/sim/src/up_idle.c

@@ -117,7 +117,7 @@ void up_idle(void)
 #endif
 
 
-#ifdef CONFIG_NET
+#ifdef CONFIG_NET_ETHERNET
   /* Run the network if enabled */
 
   netdriver_loop();

arch/sim/src/up_initialize.c

@@ -158,7 +158,7 @@ void up_initialize(void)
   up_registerblockdevice(); /* Our FAT ramdisk at /dev/ram0 */
 #endif
 
-#ifdef CONFIG_NET
+#ifdef CONFIG_NET_ETHERNET
   netdriver_init();         /* Our "real" network driver */
 #endif