livepatch: Fix missing unlock on error in klp_enable_patch()

Add missing unlock when try_module_get() fails in klp_enable_patch().

Fixes: 5ef3dd2 ("livepatch: Fix kobject refcount bug on klp_init_patch_early failure path")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: David Vernet <void@manifault.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211225025115.475348-1-yangyingliang@huawei.com

kernel/livepatch/core.c

@@ -1047,8 +1047,10 @@ int klp_enable_patch(struct klp_patch *patch)
 		return -EINVAL;
 	}
 
-	if (!try_module_get(patch->mod))
+	if (!try_module_get(patch->mod)) {
+		mutex_unlock(&klp_mutex);
 		return -ENODEV;
+	}
 
 	klp_init_patch_early(patch);