net: ethernet: adi: adin1110: Check return value of devm_gpiod_get_optional() in adin1110_check_spi()

The devm_gpiod_get_optional() function may return an ERR_PTR in case of
genuine GPIO acquisition errors, not just NULL which indicates the
legitimate absence of an optional GPIO.

Add an IS_ERR() check after the call in adin1110_check_spi(). On error,
return the error code to ensure proper failure handling rather than
proceeding with invalid pointers.

Fixes: 36934cac7aaf ("net: ethernet: adi: adin1110: add reset GPIO")
Signed-off-by: Chen Ni <[e-mail]>
Reviewed-by: Nuno Sá <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/adi/adin1110.c

···
 
 	reset_gpio = devm_gpiod_get_optional(&priv->spidev->dev, "reset",
 					     GPIOD_OUT_LOW);
+	if (IS_ERR(reset_gpio))
+		return dev_err_probe(&priv->spidev->dev, PTR_ERR(reset_gpio),
+				     "failed to get reset gpio\n");
 	if (reset_gpio) {
 		/* MISO pin is used for internal configuration, can't have
 		 * anyone else disturbing the SDO line.