mlxbf_gige: return EPROBE_DEFER if PHY IRQ is not available

The message "Error getting PHY irq. Use polling instead"
is emitted when the mlxbf_gige driver is loaded by the
kernel before the associated gpio-mlxbf driver, and thus
the call to get the PHY IRQ fails since it is not yet
available. The driver probe() must return -EPROBE_DEFER
if acpi_dev_gpio_irq_get_by() returns the same.

Fixes: 6c2a6ddca763 ("net: mellanox: mlxbf_gige: Replace non-standard interrupt handling")
Signed-off-by: David Thompson <[e-mail]>
Reviewed-by: Asmaa Mnebhi <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c

···
 	priv->llu_plu_irq = platform_get_irq(pdev, MLXBF_GIGE_LLU_PLU_INTR_IDX);
 
 	phy_irq = acpi_dev_gpio_irq_get_by(ACPI_COMPANION(&pdev->dev), "phy", 0);
-	if (phy_irq < 0) {
-		dev_err(&pdev->dev, "Error getting PHY irq. Use polling instead");
+	if (phy_irq == -EPROBE_DEFER) {
+		err = -EPROBE_DEFER;
+		goto out;
+	} else if (phy_irq < 0) {
 		phy_irq = PHY_POLL;
 	}