hostap: Check for band and channel compatibility

If a user provides both band and channel then check if they are
compatible or not.

Also, move the multiple remove network cleanup to goto.

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