firmware: Fix a reference count leak.

kobject_init_and_add() takes reference even when it fails.
If this function returns an error, kobject_put() must be called to
properly clean up the memory associated with the object.
Callback function fw_cfg_sysfs_release_entry() in kobject_put()
can handle the pointer "entry" properly.
Signed-off-by: Qiushi Wu <wu000273@umn.edu>
Link: https://lore.kernel.org/r/20200613190533.15712-1-wu000273@umn.eduSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/firmware/qemu_fw_cfg.c

@@ -605,8 +605,10 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
 	/* register entry under "/sys/firmware/qemu_fw_cfg/by_key/" */
 	err = kobject_init_and_add(&entry->kobj, &fw_cfg_sysfs_entry_ktype,
 				   fw_cfg_sel_ko, "%d", entry->select);
-	if (err)
-		goto err_register;
+	if (err) {
+		kobject_put(&entry->kobj);
+		return err;
+	}
 
 	/* add raw binary content access */
 	err = sysfs_create_bin_file(&entry->kobj, &fw_cfg_sysfs_attr_raw);
@@ -622,7 +624,6 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
 
 err_add_raw:
 	kobject_del(&entry->kobj);
-err_register:
 	kfree(entry);
 	return err;
 }