staging: wilc1000: make use of FIELD_GET/_PREP macro

Simplified the code by making use of FIELD_GET/_PREP bitfield macro.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Link: https://lore.kernel.org/r/20200214172250.13026-2-ajay.kathat@microchip.com


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