staging: wilc1000: remove the use of scan shadow buffer

Remove scan shadow buffer, which is used to store a copy of scan
results. Instead, use cfg80211 provided API's to retrieve required
info. Remove the helper functions which are operating on shadow buffer,
as it's not require now.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>