qtnfmac: SCAN results: retreive frame type information from "IE set" TLV

"IE set" TLV carries the same information as
qlink_event_scan_result::frame_type. Convert the event to make use of
TLV and drop frame_type member.
While at it, make qlink_event_scan_result structure alignement-safe.

Signed-off-by: Igor Mitsyanko <igor.mitsyanko.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>