ata: sata_mv:- Handle return value of devm_ioremap.

Here, If devm_ioremap will fail. It will return NULL.
Then hpriv->base = NULL - 0x20000; Kernel can run into
a NULL-pointer dereference. This error check will avoid
NULL pointer dereference.
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org

drivers/ata/sata_mv.c

@@ -4132,6 +4132,9 @@ static int mv_platform_probe(struct platform_device *pdev)
 	host->iomap = NULL;
 	hpriv->base = devm_ioremap(&pdev->dev, res->start,
 				   resource_size(res));
+	if (!hpriv->base)
+		return -ENOMEM;
+
 	hpriv->base -= SATAHC0_REG_BASE;
 
 	hpriv->clk = clk_get(&pdev->dev, NULL);