hostapd: disable support for Wired Equivalent Privacy by default

hostapd: disable support for Wired Equivalent Privacy by default

Upstream in commit 200c7693c9a1 ("Make WEP functionality an optional
build parameter") has made WEP functionality an optional build parameter
disabled as default, because WEP should not be used for anything
anymore. As a step towards removing it completely, they moved all WEP
related functionality behind CONFIG_WEP blocks and disabled it by
default.

This functionality is subject to be completely removed in a future
release.

So follow this good security advice, deprecation notice and disable WEP
by default, but still allow custom builds with WEP support via
CONFIG_WPA_ENABLE_WEP config option till upstream removes support for
WEP completely.

Signed-off-by: Petr Štetiar <ynezz@true.cz>