smb3: correct smb3 ACL security descriptor

Address warning:

        fs/smbfs_client/smb2pdu.c:2425 create_sd_buf()
        warn: struct type mismatch 'smb3_acl vs cifs_acl'

Pointed out by Dan Carpenter via smatch code analysis tool

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>