gpio: of: Fix logic inversion

The SPI chip selects were not properly inspected due to
a logic inversion. This made SPI GPIOs not work.

Cc: Jan Kotas <jank@cadence.com>
Reported-by: Jan Kotas <jank@cadence.com>
Tested-by: Jan Kotas <jank@cadence.com>
Fixes: f3186dd8 ("spi: Optionally use GPIO descriptors for CS GPIOs")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/gpio/gpiolib-of.c

@@ -125,7 +125,7 @@ static void of_gpio_flags_quirks(struct device_node *np,
 
 		for_each_child_of_node(np, child) {
 			ret = of_property_read_u32(child, "reg", &cs);
-			if (!ret)
+			if (ret)
 				continue;
 			if (cs == index) {
 				/*