mesh: Set correct address for mesh default broadcast/multicast keys

mesh: Set correct address for mesh default broadcast/multicast keys

wpa_drv_set_key() was called with a NULL address for IGTK and MGTK
before this patch. The nl80211 driver will then not add the
NL80211_KEY_DEFAULT_TYPE_MULTICAST flag for the key, which wrongly marks
this key also as a default unicast key in the Linux kernel.

With SAE this is no real problem in practice, as a pairwise key will be
negotiated in mesh mode, before the first data frame gets send. When
using IEEE 802.1X in a mesh network in the future, this gets a problem,
as Linux now will encrypt EAPOL frames with the default key, which is
also marked for unicast usage without this patch.

Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>