staging: wilc1000: replace semaphore sem_get_rssi with a completion

staging: wilc1000: replace semaphore sem_get_rssi with a completion

Semaphore sem_get_rssi is used to signal completion of its host
interface message. Since the thread locking this semaphore will have
to wait, completions are the preferred mechanism and will offer a
performance improvement.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>