[CIFS] SMB3 Signing enablement

SMB3 uses a much faster method of signing (which is also better in other ways),
AES-CMAC.  With the kernel now supporting AES-CMAC since last release, we
are overdue to allow SMB3 signing (today only CIFS and SMB2 and SMB2.1,
but not SMB3 and SMB3.1 can sign) - and we need this also for checking
secure negotation and also per-share encryption (two other new SMB3 features
which we need to implement).

This patch needs some work in a few areas - for example we need to
move signing for SMB2/SMB3 from per-socket to per-user (we may be able to
use the "nosharesock" mount option in the interim for the multiuser case),
and Shirish found a bug in the earlier authentication overhaul
(setting signing flags properly) - but those can be done in followon
patches.

Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 2906ee2..603f18a 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -10,6 +10,7 @@
 	select CRYPTO_ECB
 	select CRYPTO_DES
 	select CRYPTO_SHA256
+	select CRYPTO_CMAC
 	help
 	  This is the client VFS module for the Common Internet File System
 	  (CIFS) protocol which is the successor to the Server Message Block