Bluetooth: use wait_event API instead of open-coding it

I've seen timeout errors from HCI commands where it looks like
schedule_timeout() has returned immediately; additional logging for the
error case gives:

	req_status=1 req_result=0 remaining=10000 jiffies

so the device is still in state HCI_REQ_PEND and the value returned by
schedule_timeout() is the same as the original timeout (HCI_INIT_TIMEOUT
on a system with HZ=1000).

Use wait_event_interruptible_timeout() instead of open-coding similar
behaviour which is subject to the spurious failure described above.

Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>