efi_memory: return MapKey

efi_get_memory_map should set a defined value for map_key.

We later can introduce the test against this value in
efi_exit_boot_services as required by the UEFI standard.
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: NAlexander Graf <agraf@suse.de>

lib/efi_loader/efi_memory.c

@@ -431,6 +431,8 @@ efi_status_t efi_get_memory_map(unsigned long *memory_map_size,
 		}
 	}
 
+	*map_key = 0;
+
 	return EFI_SUCCESS;
 }