RISC-V: Clean up some GENERIC options

Some of the config options that are disabled by default seem to be only
for historical reasons. Enable those that appear to no longer be
problematic. This includes WITH_CTF, STACK, GEOM_RAID, and re-enabling
blacklisted kernel modules.

Reviewed by: markj
Approved by: markj (mentor)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D20495