cc2520: update initial transmit power value

CC2520 has the default 0dBm transmit power level  on reset.
This patch update initial value of transmit power with 0dBm value.
Signed-off-by: NVarka Bhadram <varkab@cdac.in>
Cc: Brad Campbell <bradjc5@gmail.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

drivers/net/ieee802154/cc2520.c

@@ -755,9 +755,11 @@ static int cc2520_register(struct cc2520_private *priv)
 	if (!priv->amplified) {
 		priv->hw->phy->supported.tx_powers = cc2520_powers;
 		priv->hw->phy->supported.tx_powers_size = ARRAY_SIZE(cc2520_powers);
+		priv->hw->phy->transmit_power = priv->hw->phy->supported.tx_powers[4];
 	} else {
 		priv->hw->phy->supported.tx_powers = cc2520_cc2591_powers;
 		priv->hw->phy->supported.tx_powers_size = ARRAY_SIZE(cc2520_cc2591_powers);
+		priv->hw->phy->transmit_power = priv->hw->phy->supported.tx_powers[0];
 	}
 
 	dev_vdbg(&priv->spi->dev, "registered cc2520\n");