[CIFS] implement upcalls for SPNEGO blob via keyctl API

Add routines to handle upcalls to userspace via keyctl for the purpose
of getting a SPNEGO blob for a particular uid and server combination.

Clean up the Makefile a bit and set it up to only compile cifs_spnego
if CONFIG_CIFS_UPCALL is set. Also change CONFIG_CIFS_UPCALL to depend
on CONFIG_KEYS rather than CONFIG_CONNECTOR.

cifs_spnego.h defines the communications between kernel and userspace
and is intended to be shared with userspace programs.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/Kconfig b/fs/Kconfig
index cc28a69..e431c38 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -2007,7 +2007,7 @@
 config CIFS_UPCALL
 	  bool "Kerberos/SPNEGO advanced session setup (EXPERIMENTAL)"
 	  depends on CIFS_EXPERIMENTAL
-	  depends on CONNECTOR
+	  depends on KEYS
 	  help
 	    Enables an upcall mechanism for CIFS which will be used to contact
 	    userspace helper utilities to provide SPNEGO packaged Kerberos