dmaengine: ti: omap-dma: don't allow a null od->plat pointer to be dereferenced

Currently when the call to dev_get_platdata returns null the driver issues
a warning and then later dereferences the null pointer.  Avoid this issue
by returning -ENODEV error rather when the platform data is null and
change the warning to an appropriate error message.

Addresses-Coverity: ("Dereference after null check")
Fixes: 211010ae ("dmaengine: ti: omap-dma: Pass sdma auxdata to driver and use it")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/dma/ti/omap-dma.c

@@ -1658,8 +1658,10 @@ static int omap_dma_probe(struct platform_device *pdev)
 	if (conf) {
 		od->cfg = conf;
 		od->plat = dev_get_platdata(&pdev->dev);
-		if (!od->plat)
-			dev_warn(&pdev->dev, "no sdma auxdata needed?\n");
+		if (!od->plat) {
+			dev_err(&pdev->dev, "omap_system_dma_plat_info is missing");
+			return -ENODEV;
+		}
 	} else {
 		od->cfg = &default_cfg;