extres/syscon: Commit missing bits from r327106

r327106 introduced kobj to syscon so it can be subclassed and fit in with
the rest of the syscon framework. The diff for syscon.c was misapplied in a
clean tree prior to commit, so bring it back to what was included in the
review and tested. The entire file has basically been rewritten from what
was present prior to the kobj work.

Pointy hat to: me