hostap: Convert the unsupported event to warning

This is a implementation gap and shouldn't be exposed to customers.
But when we run with debug it still helps to identify any important
events that are not handled.

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