libpmc: Explicitly whitelist json fields

Adds all missing Intel fields and turns jevents.c into an explicit white
list mechanism so that we no longer ignore important fields that often
invalidate the counter. The json event parser must now parse every
field on each architecture that we support. This has been tested by
running tinderbox and manually running jevent against our current json
repository. As a bonus I fixed spelling errors in the AMD JSON
definitions.

Sponsored by: Netflix

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/2055