ieee802154/at86rf230: Fix typo unkown -> unknown

Signed-off-by: NStefan Schmidt <s.schmidt@samsung.com>
Acked-by: NAlexander Aring <alex.aring@gmail.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

drivers/net/ieee802154/at86rf230.c

@@ -1474,7 +1474,7 @@ at86rf230_detect_device(struct at86rf230_local *lp)
 		lp->hw->phy->symbol_duration = 16;
 		break;
 	default:
-		chip = "unkown";
+		chip = "unknown";
 		rc = -ENOTSUPP;
 		break;
 	}