sky2: fix missing register reset on error path in sky2_test_msi()

In sky2_test_msi() the temporarily set SW IRQ in B0 register is not reset in case
that request_irq() fails.
With this patch we only set the interrupt mask if request_irq() was successful.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/sky2.c

@@ -4804,14 +4804,14 @@ static int __devinit sky2_test_msi(struct sky2_hw *hw)
 
 	init_waitqueue_head(&hw->msi_wait);
 
-	sky2_write32(hw, B0_IMSK, Y2_IS_IRQ_SW);
-
 	err = request_irq(pdev->irq, sky2_test_intr, 0, DRV_NAME, hw);
 	if (err) {
 		dev_err(&pdev->dev, "cannot assign irq %d\n", pdev->irq);
 		return err;
 	}
 
+	sky2_write32(hw, B0_IMSK, Y2_IS_IRQ_SW);
+
 	sky2_write8(hw, B0_CTST, CS_ST_SW_IRQ);
 	sky2_read8(hw, B0_CTST);