cifs: minor simplification to smb2_is_network_name_deleted

Trivial change to clarify code in smb2_is_network_name_deleted

Suggested-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>