rtlwifi: rtl8192su: Fix problem connecting to HT-enabled AP

The driver fails to connect to 802.11n-enabled APs. The patch fixes
Bug #42262.

Signed-off-by: George <george0505@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@kernel.org>        [2.6.39+]
Signed-off-by: John W. Linville <linville@tuxdriver.com>