mmc: dw_mmc-pltfm: fix the potential NULL pointer dereference

BugLink: http://bugs.launchpad.net/bugs/1642572

commit 45c7a490 upstream.

platform_get_resource can be returned the NULL pointer.
Then regs->start should be referred to NULL Pointer.
devm_ioremap_resource() checks whether res is NULL or not.
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/mmc/host/dw_mmc-pltfm.c

@@ -59,12 +59,13 @@ int dw_mci_pltfm_register(struct platform_device *pdev,
 	host->pdata = pdev->dev.platform_data;
 
 	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	/* Get registers' physical base address */
-	host->phy_regs = regs->start;
 	host->regs = devm_ioremap_resource(&pdev->dev, regs);
 	if (IS_ERR(host->regs))
 		return PTR_ERR(host->regs);
 
+	/* Get registers' physical base address */
+	host->phy_regs = regs->start;
+
 	platform_set_drvdata(pdev, host);
 	return dw_mci_probe(host);
 }