mac80211_hwsim: fix possible memory leak in hwsim_new_radio_nl()

mac80211_hwsim: fix possible memory leak in hwsim_new_radio_nl()

CVE-2018-8087

'hwname' is malloced in hwsim_new_radio_nl() and should be freed
before leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: ff4dd73dd2b4 ("mac80211_hwsim: check HWSIM_ATTR_RADIO_NAME length")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
(cherry-picked from 0ddcff49b672239dda94d70d0fcf50317a9f4b51)
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Acked-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>