pstore: Inform unregistered backend names as well

Currently we only show the registered ones in the kernel
log; users that change backend for some reason require
first to unregister the current one, so let's confirm this
operation with a message in the log.
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221006224212.569555-4-gpiccoli@igalia.com

fs/pstore/platform.c

@@ -665,6 +665,8 @@ void pstore_unregister(struct pstore_info *psi)
 	psinfo = NULL;
 	kfree(backend);
 	backend = NULL;
+
+	pr_info("Unregistered %s as persistent store backend\n", psi->name);
 	mutex_unlock(&psinfo_lock);
 }
 EXPORT_SYMBOL_GPL(pstore_unregister);