staging: wilc1000: txq_thread_started: replaces a semaphore with a completion

This patch replaces a semaphore(txq_thread_started) with a completion.
Struct semaphore txq_thread_started is used to signal completion of txq thread.
It is better to use completion than semaphore for this case.

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>