bluez4: enable hard-wired bluetooth adapter on ttyO1

This retains upstream behavior of bluetooth being disabled, but adds the hooks necessary so that "systemctl enable bluetooth.service" also ensures the bluetooth-ttyO1.service is enabled automatically.  Seems to work nicely for me.

Gumstix COMs that have the Wi2Wi module provide bluetooth support through an
HCI/UART interface directly connected to the CPU's ttyO1 serial port.  This
additional service enables that interface when bluetooth is enabled.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>