mac80211_hwsim: add concurrent channels scanning support over virtio

This fixed the crash when setting channels to 2 or more when
communicating over virtio.

Signed-off-by: Weilun Du <wdu@google.com>
Link: https://lore.kernel.org/r/20210506180530.3418576-1-wdu@google.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>