smb: use LIST_HEAD() to simplify code

list_head can be initialized automatically with LIST_HEAD()
instead of calling INIT_LIST_HEAD(). No functional impact.

Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Steve French <stfrench@microsoft.com>