libpmc: add some AMD pmu counter aliases

Make it mostly compatible with what's defined for Intel. Except where
noted, these are defined for all of amdzen(1|2|3).

Reviewed by: emaste
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D32162

(cherry picked from commit a20c10893eb17e281f119d1b9b39c175dbf4d7bd)