staging: wlan-ng: Fix clamping of returned SSID length

commit 811a37effdb11e54e1ff1ddaa944286c88f58487 upstream.

Commit 2e254212 broke listing of available network names, since it
clamped the length of the returned SSID to WLAN_BSSID_LEN (6) instead of
WLAN_SSID_MAXLEN (32).

https://bugzilla.kernel.org/show_bug.cgi?id=52501

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>