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It is specific to MSM host with BCM BT chips in its current form.  On Tx,
the wake_peer hook is called by the serial core to wake up the serial
driver and to toggle the dev wake gpio.  On Rx, the driver listens to the
host_wake gpio state to also wake up the serial driver to receive incoming data.

The driver is also registerd to handle rfkill state changes.

Change-Id: I1356f64e9c6f42a24a09f39c4f8a5258e93de602