staging: wilc1000: move firmware API struct's to separate header file

It's recommended to keep the 'struct' used for passing data to firmware
in separate header file. So added 'fw.h' header file to keep struct's
used to pass data to firmware.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Link: https://lore.kernel.org/r/20200117160157.8706-3-ajay.kathat@microchip.com


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