rtlwifi: rtl8192cu: Fix performance issue.

After physical reconnect, the rtl8192cu chipset shows low
transmission rates.It cause is that variable "iqk_initialized"
do not de-initialized. So I add this code.

Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>