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 --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index a08306a..8029301 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -9,6 +9,7 @@
 	select CRYPTO_ARC4
 	select CRYPTO_ECB
 	select CRYPTO_DES
+	select CRYPTO_SHA256
 	help
 	  This is the client VFS module for the Common Internet File System
 	  (CIFS) protocol which is the successor to the Server Message Block