net: phy: phylink: Don't release NULL GPIO

If CONFIG_GPIOLIB is disabled, gpiod_put() becomes a stub that produces a
warning, this helped identify that we could be attempting to release a NULL
pl->link_gpio GPIO descriptor, so guard against that.

Fixes: daab334 ("net: phy: phylink: Release link GPIO")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phylink.c

@@ -624,7 +624,7 @@ void phylink_destroy(struct phylink *pl)
 {
 	if (pl->sfp_bus)
 		sfp_unregister_upstream(pl->sfp_bus);
-	if (!IS_ERR(pl->link_gpio))
+	if (!IS_ERR_OR_NULL(pl->link_gpio))
 		gpiod_put(pl->link_gpio);
 
 	cancel_work_sync(&pl->resolve);