spi: octeon: use devm_platform_ioremap_resource() to simplify code

Use devm_platform_ioremap_resource() to simplify the code a bit.
This is detected by coccinelle.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190904135918.25352-10-yuehaibing@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-cavium-octeon.c

@@ -18,7 +18,6 @@
 
 static int octeon_spi_probe(struct platform_device *pdev)
 {
-	struct resource *res_mem;
 	void __iomem *reg_base;
 	struct spi_master *master;
 	struct octeon_spi *p;
@@ -30,8 +29,7 @@ static int octeon_spi_probe(struct platform_device *pdev)
 	p = spi_master_get_devdata(master);
 	platform_set_drvdata(pdev, master);
 
-	res_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	reg_base = devm_ioremap_resource(&pdev->dev, res_mem);
+	reg_base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(reg_base)) {
 		err = PTR_ERR(reg_base);
 		goto fail;