ieee820154: add max csma backoffs setting support

This patch add support for max csma backoffs setting via nl802154
framework.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
index 27e98d1..79b9ae0 100644
--- a/include/net/cfg802154.h
+++ b/include/net/cfg802154.h
@@ -45,6 +45,9 @@
 	int	(*set_backoff_exponent)(struct wpan_phy *wpan_phy,
 					struct wpan_dev *wpan_dev, u8 min_be,
 					u8 max_be);
+	int	(*set_max_csma_backoffs)(struct wpan_phy *wpan_phy,
+					 struct wpan_dev *wpan_dev,
+					 u8 max_csma_backoffs);
 };
 
 struct wpan_phy {