ptp: ixp46x: remove NO_IRQ handling

gpio_to_irq does not return NO_IRQ but instead returns a negative
error code on failure. Returning NO_IRQ from the function has no
negative effects as we only compare the result to the expected
interrupt number, but it's better to return a proper failure
code for consistency, and we should remove NO_IRQ from the kernel
entirely.

Signed-off-by: Arnd Bergmann <[e-mail]>
Acked-by: Richard Cochran <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/ptp/ptp_ixp46x.c

···
 		return err;
 
 	irq = gpio_to_irq(gpio);
+	if (irq < 0)
+		return irq;
 
-	if (NO_IRQ == irq)
-		return NO_IRQ;
-
-	if (irq_set_irq_type(irq, IRQF_TRIGGER_FALLING)) {
+	err = irq_set_irq_type(irq, IRQF_TRIGGER_FALLING);
+	if (err) {
 		pr_err("cannot set trigger type for irq %d\n", irq);
-		return NO_IRQ;
+		return err;
 	}
 
-	if (request_irq(irq, isr, 0, DRIVER, &ixp_clock)) {
+	err = request_irq(irq, isr, 0, DRIVER, &ixp_clock);
+	if (err) {
 		pr_err("request_irq failed for irq %d\n", irq);
-		return NO_IRQ;
+		return err;
 	}
 
 	return irq;