staging: vt6655: delete non-standard ioctl 0xFF

Custom ioctl 0xff is legacy code that was used for
patched version of wpa_supplicant,  where function
wpa_authen_Status_transfer() called this ioctl  to
tell authentication   status to  the driver. While
from upstream  was added only driver code  to  the
kernel  but  not  patches to the wpa_supplicant we
can safely remove this unused ioctl.

Signed-off-by: Vladimir A. Nazarenko <naszar@ya.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>