staging: rtl8192e: remove dead private call to _rtl92e_ioctl.

A RTL_IOCTL_WPA_SUPPLICANT call is a proprietary version of
wpa supplicant.

All kernel calls use SIOCSIWENCODEEXT call via wireless handlers
already used in this driver.

Remove dead code.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>