efi_loader: export root node handle

This is a preparatory patch.
The root node handle will be used as a dummy parent handle when invoking
an EFI image from bootefi/bootmgr command.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>

Rebased.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/include/efi_loader.h b/include/efi_loader.h
index f7bf732..93f7672 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -25,6 +25,9 @@
 	EFI_GUID(0xe61d73b9, 0xa384, 0x4acc, \
 		 0xae, 0xab, 0x82, 0xe8, 0x28, 0xf3, 0x62, 0x8b)
 
+/* Root node */
+extern efi_handle_t efi_root;
+
 int __efi_entry_check(void);
 int __efi_exit_check(void);
 const char *__efi_nesting(void);