[iscsi] Include DHCP server address in iBFT

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/block/ibft.c

 	ibft_set_ipaddr_setting ( NULL, &nic->dns[0], &dns_setting,
 				  ( sizeof ( nic->dns ) /
 				    sizeof ( nic->dns[0] ) ) );
+	ibft_set_ipaddr_setting ( parent, &nic->dhcp, &dhcp_server_setting, 1 );
 	DBG ( "iBFT NIC DNS = %s", ibft_ipaddr ( &nic->dns[0] ) );
 	DBG ( ", %s\n", ibft_ipaddr ( &nic->dns[1] ) );
 	if ( ( rc = ibft_set_string_setting ( NULL, strings, &nic->hostname,

src/include/ipxe/settings.h

 asset_setting __setting ( SETTING_HOST_EXTRA, asset );
 extern const struct setting
 board_serial_setting __setting ( SETTING_HOST_EXTRA, board-serial );
+extern const struct setting dhcp_server_setting __setting ( SETTING_MISC,
+							    dhcp-server );
 
 /**
  * Initialise a settings block