CIFS: Enable encryption during session setup phase

commit cabfb3680f78981d26c078a26e5c748531257ebb upstream.

In order to allow encryption on SMB connection we need to exchange
a session key and generate encryption and decryption keys.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Cc: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>