net: mvmdio: Check for a valid interrupt instead of an error

The following commit:

commit 9ec36cafe43bf835f8f29273597a5b0cbc8267ef
Author: Rob Herring <robh@kernel.org>
Date:   Wed Apr 23 17:57:41 2014 -0500

    of/irq: do irq resolution in platform_get_irq

changed platform_get_irq() which now returns EINVAL and EPROBE_DEFER,
in addition to ENXIO. If there's no interrupt for mvmdio, platform_get_irq()
returns EINVAL, but we currently check only for ENXIO.

Fix this by looking for a positive integer, which is the proper way of
validating a virtual interrupt number.

While at it, add a proper handling for the deferral probe case.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Reviewed-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvmdio.c

@@ -232,7 +232,7 @@ static int orion_mdio_probe(struct platform_device *pdev)
 		clk_prepare_enable(dev->clk);
 
 	dev->err_interrupt = platform_get_irq(pdev, 0);
-	if (dev->err_interrupt != -ENXIO) {
+	if (dev->err_interrupt > 0) {
 		ret = devm_request_irq(&pdev->dev, dev->err_interrupt,
 					orion_mdio_err_irq,
 					IRQF_SHARED, pdev->name, dev);
@@ -241,6 +241,9 @@ static int orion_mdio_probe(struct platform_device *pdev)
 
 		writel(MVMDIO_ERR_INT_SMI_DONE,
 			dev->regs + MVMDIO_ERR_INT_MASK);
+
+	} else if (dev->err_interrupt == -EPROBE_DEFER) {
+		return -EPROBE_DEFER;
 	}
 
 	mutex_init(&dev->lock);