staging: wlan-ng: Release struct returned by cfg80211_inform_bss to avoid potential memory leak.

Function cfg80211_inform_bss returns a pointer to a referenced struct cfg80211_bss
but no information is needed from this struct in function prism2_scan and therefore
we release it by calling cfg80211_put_bss.

Signed-off-by: Krzysztof Wilczynski <krzysztof.wilczynski@linux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>