Revert r289096:

Files listed in 'CONFS' are not properly included in new
installations (missing from base.txz), for reasons I still
do not fully understand.

This reverts the change excluding /etc/ppp/ppp.conf from
a new installation. /etc/dma/dma.conf is also affected,
but requires a different solution, still being investigated.

Reported by: Ben Woods
Sponsored by: The FreeBSD Foundation