hwrng: stm32 - fix unbalanced pm_runtime_enable

BugLink: https://bugs.launchpad.net/bugs/1855313

commit af0d4442 upstream.

No remove function implemented yet in the driver.
Without remove function, the pm_runtime implementation
complains when removing and probing again the driver.
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/char/hw_random/stm32-rng.c

@@ -166,6 +166,13 @@ static int stm32_rng_probe(struct platform_device *ofdev)
 	return devm_hwrng_register(dev, &priv->rng);
 }
 
+static int stm32_rng_remove(struct platform_device *ofdev)
+{
+	pm_runtime_disable(&ofdev->dev);
+
+	return 0;
+}
+
 #ifdef CONFIG_PM
 static int stm32_rng_runtime_suspend(struct device *dev)
 {
@@ -202,6 +209,7 @@ static struct platform_driver stm32_rng_driver = {
 		.of_match_table = stm32_rng_match,
 	},
 	.probe = stm32_rng_probe,
+	.remove = stm32_rng_remove,
 };
 
 module_platform_driver(stm32_rng_driver);