Speed up wlan availability if mac address file is missing

- Reduce the timeout for loading to 5s, to match with the previous
driver from Android
- Use request_firmware_direct to load the MAC address file, it may not
exist (e.g. DVT Dev Board hardware), and it's not going to magically
appear, so don't waste a minute waiting on the userspace helper.

Change-Id: If9dbffff8bfb2c84e6fd213303437baff07ec567