at86rf230: add force slotted operation bit

This patch adds a force setting of slotted operation bit. The atben
chips sometimes set these bit. The reason is unknown. Nevertheless we
don't support slotted operation so we set this bit now force while
probing.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/net/ieee802154/at86rf230.c

@@ -1358,6 +1358,14 @@ static int at86rf230_hw_init(struct at86rf230_local *lp)
 		return -EINVAL;
 	}
 
+	/* Force setting slotted operation bit to 0. Sometimes the atben
+	 * sets this bit and I don't know why. We set this always force
+	 * to zero while probing.
+	 */
+	rc = at86rf230_write_subreg(lp, SR_SLOTTED_OPERATION, 0);
+	if (rc)
+		return rc;
+
 	return 0;
 }