ieee802154/at86rf230: Fix typo unkown -> unknown

Signed-off-by: Stefan Schmidt <s.schmidt@samsung.com>
Acked-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/drivers/net/ieee802154/at86rf230.c b/drivers/net/ieee802154/at86rf230.c
index 3523d9e..2f66b8a 100644
--- a/drivers/net/ieee802154/at86rf230.c
+++ b/drivers/net/ieee802154/at86rf230.c
@@ -1474,7 +1474,7 @@
 		lp->hw->phy->symbol_duration = 16;
 		break;
 	default:
-		chip = "unkown";
+		chip = "unknown";
 		rc = -ENOTSUPP;
 		break;
 	}