Moved index of analog input used in test from source
code to Kconfig option to simplify adding new targets.
Signed-off-by: Michał Stasiak <michal.stasiak@nordicsemi.no>
Tests use nordic specific comparator api which enable it's
runtime reconfiguration.
As there were no tests prepared when introducing this api,
PR adds some to extend test coverage.
Signed-off-by: Bartlomiej Buczek <bartlomiej.buczek@nordicsemi.no>