client: Add set-advertise-tx-power command

This adds set-advertise-tx-power which can be used include TX power
in the advertisement data:

set-advertise-manufacturer <on/off>
[bluetooth]# set-advertise-tx-power on
[bluetooth]# advertise on

@ Advertising Added: 1
< HCI Command: LE Set Aidvertising Data (0x08|0x0008) plen 32
        Length: 6
        Flags: 0x02
          LE General Discoverable Mode
        TX power: 9 dBm
2 files changed