cifs: fix mount on old smb servers

The client was sending rfc1002 session request packet with a wrong
length field set, therefore failing to mount shares against old SMB
servers over port 139.

Fix this by calculating the correct length as specified in rfc1002.

Fixes: d7173623

 ("cifs: use ALIGN() and round_up() macros")
Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>