pcmcia: at91_cf: Use PTR_ERR_OR_ZERO()

Fix ptr_ret.cocci warnings:
drivers/pcmcia/at91_cf.c:239:1-3: WARNING: PTR_ERR_OR_ZERO can be used

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci
Signed-off-by: Vasyl Gomonovych <gomonovych@gmail.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/pcmcia/at91_cf.c

@@ -236,10 +236,8 @@ static int at91_cf_dt_init(struct platform_device *pdev)
 	pdev->dev.platform_data = board;
 
 	mc = syscon_regmap_lookup_by_compatible("atmel,at91rm9200-sdramc");
-	if (IS_ERR(mc))
-		return PTR_ERR(mc);
 
-	return 0;
+	return PTR_ERR_OR_ZERO(mc);
 }
 #else
 static int at91_cf_dt_init(struct platform_device *pdev)