cifs: store the real expected sequence number in the mid

Currently, the signing routines take a pointer to a place to store the
expected sequence number for the mid response. It then stores a value
that's one below what that sequence number should be, and then adds one
to it when verifying the signature on the response.

Increment the sequence number before storing the value in the mid, and
eliminate the "+1" when checking the signature.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Steve French <smfrench@gmail.com>