staging: wfx: add support for start-up indication

Once firmware is loaded, it send a first indication to host. This
indication signalize that host can start to communicate with firmware.
In add, it contains information about chip and firmware (MAC addresses,
firmware version, etc...).

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20190919142527.31797-10-Jerome.Pouiller@silabs.com


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