net: fec: restore handling of PHY reset line as optional

Conversion of the driver to gpiod API done in 468ba54b ("fec:
convert to gpio descriptor") incorrectly made reset line mandatory and
resulted in aborting driver probe in cases where reset line was not
specified (note: this way of specifying PHY reset line is actually
deprecated).

Switch to using devm_gpiod_get_optional() and skip manipulating reset
line if it can not be located.

Fixes: 468ba54b ("fec: convert to gpio descriptor")
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Tested-by: Marc Kleine-Budde <mkl@pengutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230201215320.528319-1-dmitry.torokhov@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/freescale/fec_main.c

@@ -4056,12 +4056,15 @@ static int fec_reset_phy(struct platform_device *pdev)
 
 	active_high = of_property_read_bool(np, "phy-reset-active-high");
 
-	phy_reset = devm_gpiod_get(&pdev->dev, "phy-reset",
+	phy_reset = devm_gpiod_get_optional(&pdev->dev, "phy-reset",
 			active_high ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW);
 	if (IS_ERR(phy_reset))
 		return dev_err_probe(&pdev->dev, PTR_ERR(phy_reset),
 				     "failed to get phy-reset-gpios\n");
 
+	if (!phy_reset)
+		return 0;
+
 	if (msec > 20)
 		msleep(msec);
 	else