ixgbe: clear RNBC only for 82598

RNBC (0x03FC0) is only for 82598 and has different meaning
on newer HW. Make sure to only clear it for 82598.

Signed-off-by: Emil Tantilov <[e-mail]>
Tested-by: Phil Schmitt <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>

drivers/net/ethernet/intel/ixgbe/ixgbe_common.c

···
 	IXGBE_READ_REG(hw, IXGBE_GORCH);
 	IXGBE_READ_REG(hw, IXGBE_GOTCL);
 	IXGBE_READ_REG(hw, IXGBE_GOTCH);
-	for (i = 0; i < 8; i++)
-		IXGBE_READ_REG(hw, IXGBE_RNBC(i));
+	if (hw->mac.type == ixgbe_mac_82598EB)
+		for (i = 0; i < 8; i++)
+			IXGBE_READ_REG(hw, IXGBE_RNBC(i));
 	IXGBE_READ_REG(hw, IXGBE_RUC);
 	IXGBE_READ_REG(hw, IXGBE_RFC);
 	IXGBE_READ_REG(hw, IXGBE_ROC);