staging: wfx: implement 802.11 key handling

wfx_set_key() mostly copy bytes on correct offsets. A big piece of code
for a simple work. Unfortunately, I did not found any way to factorize
it.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20190919142527.31797-20-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>