cifs: clean up length checks in check2ndT2

Thus spake David Howells:

The code that follows this:

  	remaining = total_data_size - data_in_this_rsp;
	if (remaining == 0)
		return 0;
	else if (remaining < 0) {

generates better code if you drop the 'remaining' variable and compare
the values directly.

Clean it up per his recommendation...

Reported-and-acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>