Save some punctuation by using bool type's property equivalent to
doubled negation operator.
Reported-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NMichał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>