staging: wilc1000: refactor wilc_set_wfi_drv_handler() to avoid deferred handling

Avoid handling of WID_SET_DRV_HANDLER wid command in deferred approach.
Instead of posting the wid to work queue now handle directly from the
caller context. Remove 'is_sync' parameter from the API as it's not
required anymore.

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