i2c: highlander: add IRQ check

The driver is written as if platform_get_irq() returns 0 on errors (while
actually it returns a negative error code), blithely passing these error
codes to request_irq() (which takes *unsigned* IRQ #) -- which fails with
-EINVAL. Add the necessary error check to the pre-existing *if* statement
forcing the driver into the polling mode...

Fixes: 4ad48e6a ("i2c: Renesas Highlander FPGA SMBus support")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-highlander.c

@@ -379,7 +379,7 @@ static int highlander_i2c_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, dev);
 
 	dev->irq = platform_get_irq(pdev, 0);
-	if (iic_force_poll)
+	if (dev->irq < 0 || iic_force_poll)
 		dev->irq = 0;
 
 	if (dev->irq) {