Bluetooth: Enable option to configure Max Transmission value via sockopt

With the sockopt extension we can set a per-channel MaxTx value.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 059260b..8942c2f 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -55,6 +55,7 @@
 	__u16 flush_to;
 	__u8  mode;
 	__u8  fcs;
+	__u8  max_tx;
 	__u16 txwin_size;
 };
 
@@ -340,6 +341,7 @@
 	__u8		ident;
 
 	__u8		tx_win;
+	__u8		max_tx;
 	__u8		remote_tx_win;
 	__u8		remote_max_tx;
 	__u16		retrans_timeout;