spi: fix return value check in ce4100_spi_probe()

In case of error, the function platform_device_register_full()
returns ERR_PTR() and never returns NULL. The NULL test in the
return value check should be replaced with IS_ERR().
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

drivers/spi/spi-pxa2xx-pci.c

@@ -47,8 +47,8 @@ static int ce4100_spi_probe(struct pci_dev *dev,
 	pi.size_data = sizeof(spi_pdata);
 
 	pdev = platform_device_register_full(&pi);
-	if (!pdev)
-		return -ENOMEM;
+	if (IS_ERR(pdev))
+		return PTR_ERR(pdev);
 
 	pci_set_drvdata(dev, pdev);