hwmon: pwm-fan: Use platform_get_irq_optional()

The PWM fan interrupt is optional, so we don't want an error message in
the kernel log if it wasn't specified.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://lore.kernel.org/r/20190828083411.2496-2-thierry.reding@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwmon/pwm-fan.c

@@ -304,7 +304,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, ctx);
 
-	ctx->irq = platform_get_irq(pdev, 0);
+	ctx->irq = platform_get_irq_optional(pdev, 0);
 	if (ctx->irq == -EPROBE_DEFER)
 		return ctx->irq;