mtd: elm: Use correct check on return value of pm_runtime_get_sync

The ELM driver incorrectly reagard any non-zero return value from
pm_runtime_get_sync as an error, but it may return 1 if the device
was already active. Fix to only error when return value is negative.
Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/devices/elm.c

@@ -380,7 +380,7 @@ static int elm_probe(struct platform_device *pdev)
 	}
 
 	pm_runtime_enable(&pdev->dev);
-	if (pm_runtime_get_sync(&pdev->dev)) {
+	if (pm_runtime_get_sync(&pdev->dev) < 0) {
 		ret = -EINVAL;
 		pm_runtime_disable(&pdev->dev);
 		dev_err(&pdev->dev, "can't enable clock\n");