sata_fsl: fix error handling of irq_of_parse_and_map

commit aad0b624 upstream.

irq_of_parse_and_map() returns 0 on error (the result is unsigned int),
so testing for negative result never works.
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/ata/sata_fsl.c

@@ -1338,7 +1338,7 @@ static int sata_fsl_probe(struct platform_device *ofdev)
 	host_priv->csr_base = csr_base;
 
 	irq = irq_of_parse_and_map(ofdev->dev.of_node, 0);
-	if (irq < 0) {
+	if (!irq) {
 		dev_err(&ofdev->dev, "invalid irq from platform\n");
 		goto error_exit_with_cleanup;
 	}