wil6210: add support for multiple sections in brd file

Current board file loading procedure assumes that the board file
includes only one section.
New board files can include multiple sections.
Add the ability to read multiple addresses and max size from FW
file and load multiple sections from the board file into those
addresses.

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