perf vendor events arm64: Enable JSON events for eMAG

perf vendor events arm64: Enable JSON events for eMAG

This patch adds the Ampere Computing eMAG file.  This platform follows
the ARMv8 recommended IMPLEMENTATION DEFINED events, where applicable.

Signed-off-by: Sean V Kelley <seanvk.dev@oregontracks.org>
Reviewed-by: John Garry <john.garry@huawei.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: William Cohen <wcohen@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
LPU-Reference: 20180803041811.17065-1-seanvk.dev@oregontracks.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>