staging: wilc1000: rename au8Sta_AssociatedBss element sta_info structure

This is a cleanup patch, to rename au8Sta_AssociatedBss element of
sta_info structure.
The changes fix "Avoid camelCase" issue found by checkpatch.pl script.

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