SMB3: Fix 3.11 encryption to Windows and handle encrypted smb3 tcon

Temporarily disable AES-GCM, as AES-CCM is only currently
enabled mechanism on client side.  This fixes SMB3.11
encrypted mounts to Windows.

Also the tree connect request itself should be encrypted if
requested encryption ("seal" on mount), in addition we should be
enabling encryption in 3.11 based on whether we got any valid
encryption ciphers back in negprot (the corresponding session flag is
not set as it is in 3.0 and 3.02)

Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
CC: Stable <stable@vger.kernel.org>
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index 6093e51..d28f358 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -297,7 +297,7 @@ struct smb2_encryption_neg_context {
 	__le16	DataLength;
 	__le32	Reserved;
 	__le16	CipherCount; /* AES-128-GCM and AES-128-CCM */
-	__le16	Ciphers[2]; /* Ciphers[0] since only one used now */
+	__le16	Ciphers[1]; /* Ciphers[0] since only one used now */
 } __packed;
 
 struct smb2_negotiate_rsp {