regulator: gpio: Use gpio_is_valid

Use gpio_is_valid instead of an explicit comparison with 0.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/gpio-regulator.c

@@ -322,7 +322,7 @@ static int gpio_regulator_probe(struct platform_device *pdev)
 	cfg.driver_data = drvdata;
 	cfg.of_node = np;
 
-	if (config->enable_gpio >= 0) {
+	if (gpio_is_valid(config->enable_gpio)) {
 		cfg.ena_gpio = config->enable_gpio;
 		cfg.ena_gpio_initialized = true;
 	}