ath10k: add board data download from target

The QCA9887 stores its calibration data (board.bin) inside the EEPROM of
the target. This has to be downloaded manually to allow the device to
initialize correctly.

Signed-off-by: Sven Eckelmann <sven.eckelmann@open-mesh.com>
[kvalo@qca.qualcomm.com: handle -EOPNOTSUPP and s/fetch_board_data/fetch_cal_eeprom]
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>