wil6210: support parsing brd file address from fw file

In order to allow using the same brd file across different
11ad chips, the address for loading the brd file should be
part of the FW file, instead of the brd file. The brd file is
expected to include only one section.
To allow backward compatibility the driver reads the
address from the brd file in case it is not included in the
FW file.

Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>