Staging: rtl8192u: Remove two useless lines at ieee80211_wep_null

Remove two lines at ieee80211_wep_null which checkpatch.pl reported as errors.
The first one because it has a C99 comment style and the second one because it is a void
return which is useless.
The function ieee80211_wep_null cannot be completely removed because it is exported and
used to autoload the module.

Signed-off-by: Pedro Marzo Perez <marzo.pedro@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>