efi_loader: add return to efibootmgr event group

When the image loaded by efibootmgr returns, efibootmgr
needs to clean the resources. Adding the event of returning
to efibootmgr is useful to simplify the implementation.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/include/efi_loader.h b/include/efi_loader.h
index 1fd7b0b..664dae2 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -289,6 +289,8 @@
 extern const efi_guid_t efi_guid_event_group_ready_to_boot;
 /* event group ResetSystem() invoked (before ExitBootServices) */
 extern const efi_guid_t efi_guid_event_group_reset_system;
+/* event group return to efibootmgr */
+extern const efi_guid_t efi_guid_event_group_return_to_efibootmgr;
 /* GUID of the device tree table */
 extern const efi_guid_t efi_guid_fdt;
 extern const efi_guid_t efi_guid_loaded_image;