staging: wilc1000: remove pointer variable of g_linux_wlan->txq_event

Remove variable txq_wait and txq_wait_event which are pointer varialbe
of g_linux_wlan->txq_event. No need to have extra pointer varialbe. Just use
g_linux_wlan->txq_event. Remove os_context.txq_wait_event, txq_wait and it's
related codes.

Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>