cfg80211: convert S1G beacon to scan results

The S1G beacon is an extension frame as opposed to
management frame for the regular beacon. This means we may
have to occasionally cast the frame buffer to a different
header type. Luckily this isn't too bad as scan results
mostly only care about the IEs.

Signed-off-by: Thomas Pedersen <thomas@adapt-ip.com>
Link: https://lore.kernel.org/r/20200922022818.15855-6-thomas@adapt-ip.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>