libpmc: import updated pmu-events for arm64

Thanks to the recently updated import of the jevents utility by mav@, we
can now compile the latest version of these event definitions. This
should support a wider set of common ARMv8 processors, for example, the
Cortex-A72 in the Raspberry Pi 4.

This brings this folder in sync with Linux commit 62e6eb8d5454.

Reviewed by: emaste
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D35549