nl80211: Memory leak fixed

Potential memory leak via msg pointer in nl80211_get_key() function.

Signed-off-by: Niko Jokinen <ext-niko.k.jokinen@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>