at86rf230: fix volatile regmap registers

These registers are also changed by transceiver and should be volatile
for right accessing via regmap debugfs.

Signed-off-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 795106c..b64c5c7 100644
--- a/drivers/net/ieee802154/at86rf230.c
+++ b/drivers/net/ieee802154/at86rf230.c
@@ -421,6 +421,8 @@
 	case RG_PHY_ED_LEVEL:
 	case RG_IRQ_STATUS:
 	case RG_VREG_CTRL:
+	case RG_PLL_CF:
+	case RG_PLL_DCU:
 		return true;
 	default:
 		return false;