spi: gpio: Fix copy-and-paste error

This fixes an embarrassing copy-and-paste error in the
errorpath of spi_gpio_request(): we were checking the wrong
struct member for error code right after retrieveing the
sck GPIO.

Fixes: 9b00bc7b ("spi: spi-gpio: Rewrite to use GPIO descriptors")
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-gpio.c

@@ -300,8 +300,8 @@ static int spi_gpio_request(struct device *dev,
 		*mflags |= SPI_MASTER_NO_RX;
 
 	spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
-	if (IS_ERR(spi_gpio->mosi))
-		return PTR_ERR(spi_gpio->mosi);
+	if (IS_ERR(spi_gpio->sck))
+		return PTR_ERR(spi_gpio->sck);
 
 	for (i = 0; i < num_chipselects; i++) {
 		spi_gpio->cs_gpios[i] = devm_gpiod_get_index(dev, "cs",