hostap: Move to data driven design

Instead of assuming that the array is perfectly aligned with enum, moved
to a data driven design, this decouples from the enum numbering and also
helps avoid repetition of the event string while parsing.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>
Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>