rtlwifi: Fix problem when switching connections

The driver fails to clear encryption keys making it impossible
to switch connections.

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>