ieee802154: add support for listen-before-talk in wpan_phy

Listen-before-talk is an alternative to CSMA in uncoordinated networks
and prescribed by european regulations if one wants to have a device
with radio duty cycles above 10% (or less in some bands). Add a phy
property to enable/disable LBT in the phy, including support in the
at86rf230 driver for RF212 chips.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/wpan-phy.h b/include/net/wpan-phy.h
index 47fc0c1..804e6c4 100644
--- a/include/net/wpan-phy.h
+++ b/include/net/wpan-phy.h
@@ -47,6 +47,8 @@
 	s8 transmit_power;
 	u8 cca_mode;
 
+	bool lbt;
+
 	struct device dev;
 	int idx;
 
@@ -55,6 +57,7 @@
 	void (*del_iface)(struct wpan_phy *phy, struct net_device *dev);
 
 	int (*set_txpower)(struct wpan_phy *phy, int db);
+	int (*set_lbt)(struct wpan_phy *phy, bool on);
 
 	char priv[0] __attribute__((__aligned__(NETDEV_ALIGN)));
 };