net: drivers: use bool type instead of double negation

Save some punctuation by using bool type's property equivalent to
doubled negation operator.

Reported-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index a6e379f..4312db8 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -201,9 +201,9 @@
 #define xennet_sysfs_delif(dev) do { } while (0)
 #endif
 
-static int xennet_can_sg(struct net_device *dev)
+static bool xennet_can_sg(struct net_device *dev)
 {
-	return !!(dev->features & NETIF_F_SG);
+	return dev->features & NETIF_F_SG;
 }