* Check kernel config
* Allow specifying multiple kernel packages, and also no packages
which defaults to scanning all kernel configs (it is super fast
anyway)
* Add the check to Travis CI
* Adjust existing kernel configs, so they pass the kconfig_check.
(We've had to put in a lot of defaults in the aarch64
linux-postmarketos configs, that's why the diff is a bit unclean.)
* Increase modified kernel pkgrels
