PPC: Fix default config ordering and add eTSEC for ppc64

We messed up the ordering in our default configs for PPC. The top entries
are generic entries, then come sections that indicate that features are only
in because of a special feature (such as PReP).

Fix the ordering again and while at it add eTSEC support to the ppc64 target
so that we can spawn eTSEC adapters with qemu-system-ppc64.

Signed-off-by: Alexander Graf <agraf@suse.de>