libertas: Fix problem with broken V4 firmware on CF8381

Firmware V4 on CF8381 reports region code shifted by 1 byte to left.
The following patch checks for this and handles it properly.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>