efi_loader: LoadImage() check parent image

If the parent image handle does not refer to a loaded image return
EFI_INVALID_PARAMETER.
(UEFI SCT II 2017: 3.4.1 LoadImage() - 5.1.4.1.1)

Mark our root node as a loaded image to avoid an error when using it as
parent image.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/include/efi_loader.h b/include/efi_loader.h
index d3a1d4c..07ef14b 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -187,6 +187,7 @@
  */
 enum efi_object_type {
 	EFI_OBJECT_TYPE_UNDEFINED = 0,
+	EFI_OBJECT_TYPE_U_BOOT_FIRMWARE,
 	EFI_OBJECT_TYPE_LOADED_IMAGE,
 	EFI_OBJECT_TYPE_STARTED_IMAGE,
 };