wl1251: Parse and use MAC address from supplied NVS data

This patch implements parsing MAC address from NVS data which are sent to
wl1251 chip. Calibration NVS data could contain valid MAC address and it
will be used instead of randomly generated one.

This patch also moves code for requesting NVS data from userspace to driver
initialization code to make sure that NVS data will be there at time when
permanent MAC address is needed.

Calibration NVS data for wl1251 are device specific. Every device with
wl1251 chip should have been calibrated in factory and needs to provide own
calibration data.

Default example file wl1251-nvs.bin, found in linux-firmware repository,
contains MAC address 00:00:20:07:03:09. So this MAC address is marked as
invalid as it is not real device specific address, just example one.

Format of calibration NVS data can be found at:
http://notaz.gp2x.de/misc/pnd/wl1251/nvs_map.txt



Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>