Bluetooth: Use proper invalid value for tx_power

The core specification defines 127 as the "not available" value (well,
"reserved" for BR/EDR and "not available" for LE - but essentially the
same). Therefore, instead of testing for 0 (which is in fact a valid
value) we should be using this invalid value to test if the tx_power is
available.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 6c414f4..344fea0 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -319,6 +319,9 @@
 #define HCI_FLOW_CTL_MODE_PACKET_BASED	0x00
 #define HCI_FLOW_CTL_MODE_BLOCK_BASED	0x01
 
+/* The core spec defines 127 as the "not available" value */
+#define HCI_TX_POWER_INVALID	127
+
 /* Extended Inquiry Response field types */
 #define EIR_FLAGS		0x01 /* flags */
 #define EIR_UUID16_SOME		0x02 /* 16-bit UUID, more available */