efi_loader: helper function to add EFI object to list

To avoid duplicate coding provide a helper function that
initializes an EFI object and adds it to the EFI object
list.

efi_exit() is the only place where we dereference a handle
to obtain a protocol interface. Add a comment to the function.

Suggested-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/lib/efi_loader/efi_net.c b/lib/efi_loader/efi_net.c
index 74a67c5..8c5d5b4 100644
--- a/lib/efi_loader/efi_net.c
+++ b/lib/efi_loader/efi_net.c
@@ -296,11 +296,9 @@
 		goto out_of_memory;
 
 	/* Hook net up to the device list */
-	INIT_LIST_HEAD(&netobj->parent.protocols);
-	list_add_tail(&netobj->parent.link, &efi_obj_list);
+	efi_add_handle(&netobj->parent);
 
 	/* Fill in object data */
-	netobj->parent.handle = &netobj->net;
 	r = efi_add_protocol(netobj->parent.handle, &efi_net_guid,
 			     &netobj->net);
 	if (r != EFI_SUCCESS)