pata_arasan_cf: fix IRQ check

The driver's probe() method is written as if platform_get_irq() returns 0
on error, while actually it returns a negative error code (with all the
other values considered valid IRQs). Rewrite the driver's IRQ checking code
to pass the positive IRQ #s to ata_host_activate(), propagate upstream
-EPROBE_DEFER, and set up the driver to polling mode on (negative) errors
and IRQ0 (libata treats IRQ #0 as a polling mode anyway)...

Fixes: a480167b ("pata_arasan_cf: Adding support for arasan compact flash host controller")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omprussia.ru>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/ata/pata_arasan_cf.c

@@ -818,12 +818,19 @@ static int arasan_cf_probe(struct platform_device *pdev)
 	else
 		quirk = CF_BROKEN_UDMA; /* as it is on spear1340 */
 
-	/* if irq is 0, support only PIO */
-	acdev->irq = platform_get_irq(pdev, 0);
-	if (acdev->irq)
+	/*
+	 * If there's an error getting IRQ (or we do get IRQ0),
+	 * support only PIO
+	 */
+	ret = platform_get_irq(pdev, 0);
+	if (ret > 0) {
+		acdev->irq = ret;
 		irq_handler = arasan_cf_interrupt;
-	else
+	} else	if (ret == -EPROBE_DEFER) {
+		return ret;
+	} else	{
 		quirk |= CF_BROKEN_MWDMA | CF_BROKEN_UDMA;
+	}
 
 	acdev->pbase = res->start;
 	acdev->vbase = devm_ioremap(&pdev->dev, res->start,