can: m_can: Fix runtime resume call

pm_runtime_get_sync() returns a 1 if the state of the device is already
'active'. This is not a failure case and should return a success.

Therefore fix error handling for pm_runtime_get_sync() call such that
it returns success when the value is 1.

Also cleanup the TODO for using runtime PM for sleep mode as that is
implemented.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Cc: <stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -634,10 +634,12 @@ static int m_can_clk_start(struct m_can_priv *priv)
 	int err;
 
 	err = pm_runtime_get_sync(priv->device);
-	if (err)
+	if (err < 0) {
 		pm_runtime_put_noidle(priv->device);
+		return err;
+	}
 
-	return err;
+	return 0;
 }
 
 static void m_can_clk_stop(struct m_can_priv *priv)
@@ -1688,8 +1690,6 @@ failed_ret:
 	return ret;
 }
 
-/* TODO: runtime PM with power down or sleep mode  */
-
 static __maybe_unused int m_can_suspend(struct device *dev)
 {
 	struct net_device *ndev = dev_get_drvdata(dev);