can: mcp251xfd: mcp251xfd_unregister(): simplify runtime PM handling

The mcp251xfd driver supports runtime PM enabled kernels, but also
works on !CONFIG_PM configurations.

This patch simplifies the runtime PM handling in the
mcp251xfd_unregister(). In the CONFIG_PM case, runtime PM has been
enabled in the mcp251xfd_probe() function, so we can disable it here.
For !CONFIG_PM builds call mcp251xfd_clks_and_vdd_disable() directly.

Link: https://lore.kernel.org/all/20220207131047.282110-4-mkl@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c

@@ -1768,10 +1768,10 @@ static inline void mcp251xfd_unregister(struct mcp251xfd_priv *priv)
 
 	unregister_candev(ndev);
 
-	pm_runtime_get_sync(ndev->dev.parent);
-	pm_runtime_put_noidle(ndev->dev.parent);
-	mcp251xfd_clks_and_vdd_disable(priv);
-	pm_runtime_disable(ndev->dev.parent);
+	if (pm_runtime_enabled(ndev->dev.parent))
+		pm_runtime_disable(ndev->dev.parent);
+	else
+		mcp251xfd_clks_and_vdd_disable(priv);
 }
 
 static const struct of_device_id mcp251xfd_of_match[] = {