staging: wilc1000: use GENMASK to extract wid type

Refactor code by make use of 'GENMASK' to extract the WID type from
buffer received from firmware.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Link: https://lore.kernel.org/r/20191122205153.30723-4-adham.abozaeid@microchip.com


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