gpio: mvebu: only fail on missing clk if pwm is actually to be used

The gpio IP on Armada 370 at offset 0x18180 has neither a clk nor pwm
registers. So there is no need for a clk as the pwm isn't used anyhow.
So only check for the clk in the presence of the pwm registers. This fixes
a failure to probe the gpio driver for the above mentioned gpio device.

Fixes: 757642f9 ("gpio: mvebu: Add limited PWM support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-mvebu.c

@@ -773,9 +773,6 @@ static int mvebu_pwm_probe(struct platform_device *pdev,
 				     "marvell,armada-370-gpio"))
 		return 0;
 
-	if (IS_ERR(mvchip->clk))
-		return PTR_ERR(mvchip->clk);
-
 	/*
 	 * There are only two sets of PWM configuration registers for
 	 * all the GPIO lines on those SoCs which this driver reserves
@@ -786,6 +783,9 @@ static int mvebu_pwm_probe(struct platform_device *pdev,
 	if (!res)
 		return 0;
 
+	if (IS_ERR(mvchip->clk))
+		return PTR_ERR(mvchip->clk);
+
 	/*
 	 * Use set A for lines of GPIO chip with id 0, B for GPIO chip
 	 * with id 1. Don't allow further GPIO chips to be used for PWM.