Bug 93911 reported a broken handling of the BT device, causing the
driver to get stuck in a loop enabling/disabling the device whenever
the device is deactivated by the kill switch as follows:

1. The user activated the kill switch, causing the system to generate
   a 0x90 (status change) event and disabling the BT device.
2. The driver catches the event and re-enables the BT device.
3. The system detects the device being activated, but since the kill
   switch is activated, disables the BT device (again) and generates
   a 0x90 event (again).
4. Repeat from 2.

This patch adds an extra check to verify the status of the BT device,
returning silently if it is already activated.

Also, checks and returns appropriate error values while evaluating
the AUSB and BTPO methods.
Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>