staging: wilc1000: Change interface wilc_mq_send to wilc_enqueue_cmd

Replace the interface 'wilc_mq_send' with 'wilc_enqueue_cmd'
and remove the now unused structures 'message' and 'message_queue'.
Restructure switch statement in the work queue helper function
host_if_work and remove unwanted indentation.

Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>