staging: wilc1000: flush the workqueue before deinit the host

Before deinitializing the host interface, the workqueue should be flushed
to handle any pending deferred work

Signed-off-by: Adham Abozaeid <adham.abozaeid@microchip.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20190722213837.21952-1-adham.abozaeid@microchip.com


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