spi: armada-3700: fix unsigned compare than zero on irq

spi->irq is an unsigned integer hence the check if status is less than
zero has no effect.  Fix this by replacing spi->irq with an int irq
so the less than zero compare will correctly detect errors.

Issue found with static analysis with CoverityScan, CID1388567

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Romain Perier <romain.perier@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-armada-3700.c

@@ -800,7 +800,7 @@ static int a3700_spi_probe(struct platform_device *pdev)
 	struct spi_master *master;
 	struct a3700_spi *spi;
 	u32 num_cs = 0;
-	int ret = 0;
+	int irq, ret = 0;
 
 	master = spi_alloc_master(dev, sizeof(*spi));
 	if (!master) {
@@ -846,12 +846,13 @@ static int a3700_spi_probe(struct platform_device *pdev)
 		goto error;
 	}
 
-	spi->irq = platform_get_irq(pdev, 0);
-	if (spi->irq < 0) {
-		dev_err(dev, "could not get irq: %d\n", spi->irq);
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(dev, "could not get irq: %d\n", irq);
 		ret = -ENXIO;
 		goto error;
 	}
+	spi->irq = irq;
 
 	init_completion(&spi->done);