spi/s3c64xx: Check before mem-region release

Add precautionary check before releasing memory region.
Signed-off-by: NJassi Brar <jassi.brar@samsung.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/spi/spi_s3c64xx.c

@@ -1097,7 +1097,8 @@ static int s3c64xx_spi_remove(struct platform_device *pdev)
 	iounmap((void *) sdd->regs);
 
 	mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	release_mem_region(mem_res->start, resource_size(mem_res));
+	if (mem_res != NULL)
+		release_mem_region(mem_res->start, resource_size(mem_res));
 
 	platform_set_drvdata(pdev, NULL);
 	spi_master_put(master);