mtd: denali_dt: Change return value to fix smatch warning

platform_get_irq() also returns -ENXIO upon failure.
Use it instead of hardcoded return type.

Fixes the following smatch warning:
drivers/mtd/nand/denali_dt.c:93 denali_dt_probe() info:
why not propagate 'denali->irq' from platform_get_irq() instead of (-6)?

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/nand/denali_dt.c b/drivers/mtd/nand/denali_dt.c
index eb68979..067a505 100644
--- a/drivers/mtd/nand/denali_dt.c
+++ b/drivers/mtd/nand/denali_dt.c
@@ -90,7 +90,7 @@
 	denali->irq = platform_get_irq(ofdev, 0);
 	if (denali->irq < 0) {
 		dev_err(&ofdev->dev, "no irq defined\n");
-		return -ENXIO;
+		return denali->irq;
 	}
 
 	denali->flash_reg = request_and_map(&ofdev->dev, denali_reg);