wil6210: boot loader

Introduce boot loader. Instead of the operational firmware,
very small boot loader is burned to the on-board flash. Boot loader
initializes hardware upon reset, and prepares for low power mode.
Boot loader reports MAC address and detects radio chip connected.

Driver loads firmware only when bringing up interface. All information
required to set up network interface, most important is MAC address,
reported by the boot loader

The firmware composed of 2 files:
- wil6210.fw - firmware itself (compiled code + data)
- wil6210.board - board file (various board and radio dependent
  calibrations and parameters)

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>