iio: adc: at91-sama5d2_adc: remove dead code in at91_adc_probe()

From the comment of platform_get_irq(), it only returns non-zero IRQ
number and negative error number, other than zero.

Fix this by removing the if condition.
Signed-off-by: Cheng Ziqiu <chengziqiu@hust.edu.cn>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230314070130.60581-1-chengziqiu@hust.edu.cnSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/at91-sama5d2_adc.c

@@ -2400,12 +2400,8 @@ static int at91_adc_probe(struct platform_device *pdev)
 	st->dma_st.phys_addr = res->start;
 
 	st->irq = platform_get_irq(pdev, 0);
-	if (st->irq <= 0) {
-		if (!st->irq)
-			st->irq = -ENXIO;
-
+	if (st->irq < 0)
 		return st->irq;
-	}
 
 	st->per_clk = devm_clk_get(&pdev->dev, "adc_clk");
 	if (IS_ERR(st->per_clk))