testusb: Fix warning comparing pointer to 0

Avoid pointer type value compared with 0 to make code clear.

Signed-off-by: Haowen Bai <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

tools/usb/testusb.c

···
 	}
 	if (not)
 		return 0;
-	if (testdevs && testdevs->next == 0 && !device)
+	if (testdevs && !testdevs->next && !device)
 		device = testdevs->name;
 	for (entry = testdevs; entry; entry = entry->next) {
 		int	status;