CIFS: Enable signing in SMB2

Use hmac-sha256 and rather than hmac-md5 that is used for CIFS/SMB.

Signature field in SMB2 header is 16 bytes instead of 8 bytes.

Automatically enable signing by client when requested by the server
when signing ability is available to the client.

Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>

diff --cc fs/cifs/Kconfig
Simple merge

diff --cc fs/cifs/cifsencrypt.c
Simple merge

diff --cc fs/cifs/cifsglob.h
Simple merge

diff --cc fs/cifs/cifsproto.h
Simple merge

diff --cc fs/cifs/smb2glob.h
Simple merge

diff --cc fs/cifs/smb2pdu.c
Simple merge

diff --cc fs/cifs/smb2proto.h
Simple merge

diff --cc fs/cifs/smb2transport.c
Simple merge

diff --cc fs/cifs/transport.c
Simple merge