perf tools: Make the JSON parser more conformant when in strict mode

Return an error when a trailing comma is found or a new item is
encountered before a comma or an opening brace. This ensures that the
perf JSON files conform more closely to the spec at https://www.json.org

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Kajol <Jain&lt;kjain@linux.ibm.com>
Signed-off-by: James Clark <james.clark@arm.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrew.Kilroy@arm.com
Cc: John Garry <john.garry@huawei.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick.Forrington@arm.com
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20211007110543.564963-3-james.clark@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>