[netdevice] Kill off the various guess_boot_netdev() functions

Remove the assortment of miscellaneous hacks to guess the "network
boot device", and replace them each with a call to last_opened_netdev().

It still isn't guaranteed correct, but it won't be any worse than
before, and it will at least be consistent.

src/arch/i386/image/nbi.c

 	return rc;
 }
 
-/**
- * Guess boot network device
- *
- * @ret netdev		Boot network device
- */
-static struct net_device * guess_boot_netdev ( void ) {
-	struct net_device *netdev;
-
-	/* Just use the first network device */
-	for_each_netdev ( netdev ) {
-		if ( netdev->state & NETDEV_OPEN )
-			return netdev;
-	}
-
-	return NULL;
-}
-
 /**
  * Prepare DHCP parameter block for NBI image
  *
 	struct net_device *boot_netdev;
 	int rc;
 
-	boot_netdev = guess_boot_netdev();
+	boot_netdev = last_opened_netdev();
 	if ( ! boot_netdev ) {
 		DBGC ( image, "NBI %p could not identify a network device\n",
 		       image );

src/arch/i386/image/pxe_image.c

  * @ret rc		Return status code
  */
 static int pxe_exec ( struct image *image ) {
-	struct net_device *netdev;
 	int rc;
 
 	/* Ensure that PXE stack is ready to use */
 	pxe_init_structures();
 	pxe_hook_int1a();
 
-	/* Arbitrarily pick the first open network device to use for PXE */
-	for_each_netdev ( netdev ) {
-		if ( netdev->state & NETDEV_OPEN ) {
-			pxe_set_netdev ( netdev );
-			break;
-		}
-	}
+	/* Arbitrarily pick the most recently opened network device */
+	pxe_set_netdev ( last_opened_netdev() );
 
 	/* Many things will break if pxe_netdev is NULL */
 	if ( ! pxe_netdev ) {

src/arch/i386/interface/pcbios/aoeboot.c

 #include <gpxe/abft.h>
 #include <int13.h>
 
-/**
- * Guess boot network device
- *
- * @ret netdev		Boot network device
- */
-static struct net_device * guess_boot_netdev ( void ) {
-	struct net_device *netdev;
-
-	/* Just use the first network device */
-	for_each_netdev ( netdev ) {
-		if ( netdev->state & NETDEV_OPEN )
-			return netdev;
-	}
-
-	return NULL;
-}
-
 static int aoeboot ( const char *root_path ) {
 	struct ata_device ata;
 	struct int13_drive drive;
 	printf ( "AoE booting from %s\n", root_path );
 
 	/* FIXME: ugly, ugly hack */
-	struct net_device *netdev = guess_boot_netdev();
+	struct net_device *netdev = last_opened_netdev();
 
 	if ( ( rc = aoe_attach ( &ata, netdev, root_path ) ) != 0 ) {
 		printf ( "Could not attach AoE device: %s\n",

src/arch/i386/interface/pcbios/iscsiboot.c

 	.type = &setting_type_int8,
 };
 
-/**
- * Guess boot network device
- *
- * @ret netdev		Boot network device
- */
-static struct net_device * guess_boot_netdev ( void ) {
-	struct net_device *netdev;
-
-	/* Just use the first network device */
-	for_each_netdev ( netdev ) {
-		if ( netdev->state & NETDEV_OPEN )
-			return netdev;
-	}
-
-	return NULL;
-}
-
 static int iscsiboot ( const char *root_path ) {
 	struct scsi_device *scsi;
 	struct int13_drive *drive;
 	drive->blockdev = &scsi->blockdev;
 
 	/* FIXME: ugly, ugly hack */
-	struct net_device *netdev = guess_boot_netdev();
+	struct net_device *netdev = last_opened_netdev();
 	struct iscsi_session *iscsi =
 		container_of ( scsi->backend, struct iscsi_session, refcnt );
 	ibft_fill_data ( netdev, iscsi );