ath10k: rename board_data in struct ath10k

I will use board_data for something else in the following patch
so I need to rename it.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: store separate pointers for firmware data

Needed for firmware IE formatted images.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: implement firmware IE container support

Firmware IE containers can dynamically provide various information what
firmware supports. Also it can embed more than one image so updating firmware
is easy, user just needs to update one file in /lib/firmware/.

The firmware API 2 or higher will use the IE container format, the current API
1 will not use the new format but it still is supported for some time. FW API 2
files are named as firmware-2.bin (which contains both firmware and otp images)
and API 1 files are firmware.bin and otp.bin.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>