efi_loader: avoid NULL dereference in efi_dp_match

When calling bootefi hello twice a kernel dump occurs.

Neither bootefi hello nor bootefi selftest have an image
device patch. So do not try to dereference the NULL
value.

Fixes: 95c5553ea26 efi_loader: refactor boot device and loaded_image handling
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

lib/efi_loader/efi_boottime.c

@@ -1154,7 +1154,8 @@ void efi_setup_loaded_image(struct efi_loaded_image *info, struct efi_object *ob
 		(void *)&efi_device_path_to_text;
 
 	info->file_path = file_path;
-	info->device_handle = efi_dp_find_obj(device_path, NULL);
+	if (device_path)
+		info->device_handle = efi_dp_find_obj(device_path, NULL);
 
 	list_add_tail(&obj->link, &efi_obj_list);
 }