perf vendor events arm64: Revise core JSON events for eMAG

Split the PMU events into meaningful functional groups.  Update core pmu
events based on supported ARMv8 recommended IMPLEMENTATION DEFINED
events.

The JSON files are updated with reference to a PMU table shared here:

  https://github.com/AmpereComputing/ampere-centos-kernel/blob/amp-centos-7.5-kernel/Documentation/arm64/eMAG-ARM-CoreImpDefined.pdf



Changes in v3:
- Removed CHAIN event as it wouldn't be useful in Perf - William
- Will factor out events 0x00-0x38 in a follow-on patch - William
- to armv8-recommended.json
Changes in V2:
- Provided documentation for changes - John, William
- Broke up into meaningful groups - William

Signed-off-by: Sean V Kelley <seanvk.dev@oregontracks.org>
Reviewed-by: William Cohen <wcohen@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: linux-arm-kernel@lists.infradead.org
LPU-Reference: 20180916221203.7935-1-seanvk.dev@oregontracks.org
Link: https://lkml.kernel.org/n/tip-tzvs1ip6srcv2et0ny58e0wy@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>