staging: wfx: load firmware

staging: wfx: load firmware

A firmware is necessary to run the chip. wfx_init_device() is in charge
of loading firmware on chip and doing low level initialization.

Firmwares for WF200 are available here:

  https://github.com/SiliconLabs/wfx-firmware/

Note that firmware are encrypted. Driver checks that key used to encrypt
firmware match with key burned into chip.

Currently, "C0" key is used for production chips.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20190919142527.31797-6-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>