libertas: handle HOST_AWAKE event by sending WAKEUP_CONFIRM command

lbs_send_confirmwake() is a bit ugly but matches the way we confirm
sleep. We'll deal with that whole thing later.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>