hwrng: exynos - Disable runtime PM on driver unbind

Driver enabled runtime PM but did not revert this on removal. Re-binding
of a device triggered warning:
	exynos-rng 10830400.rng: Unbalanced pm_runtime_enable!

Fixes: b329669ea0b5 ("hwrng: exynos - Add support for Exynos random number generator")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/exynos-rng.c

@@ -156,6 +156,14 @@ static int exynos_rng_probe(struct platform_device *pdev)
 	return ret;
 }
 
+static int exynos_rng_remove(struct platform_device *pdev)
+{
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+
+	return 0;
+}
+
 static int __maybe_unused exynos_rng_runtime_suspend(struct device *dev)
 {
 	struct platform_device *pdev = to_platform_device(dev);
@@ -213,6 +221,7 @@ static struct platform_driver exynos_rng_driver = {
 		.of_match_table = exynos_rng_dt_match,
 	},
 	.probe		= exynos_rng_probe,
+	.remove		= exynos_rng_remove,
 };
 
 module_platform_driver(exynos_rng_driver);