re-enable squashfs parallel decompression optimization #540
Description
In cmd/gokr-build-kernel/build.go, we specify CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU. However, this value has no effect anymore since torvalds/linux@80f7840, which renamed the kernel option.
We should update the config addendum to the intended name and ensure that all options we set in the addendum are actually present in the resulting config as a safe-guard.