These units are also present in the initrd, so instead of an assert,
just use a condition so they are skipped where they need to be skipped.
Fixes https://github.com/systemd/systemd/issues/26358
If everything points to the fact that TPM2 should work, but then the
driver fails to initialize we should handle this gracefully and not
cause failing services all over the place.
Fixes: #25700