perf jevents: Add support for parsing perchip/percore events

Initially, every time we want to add new terms like chip, core thread etc,
we need to create corrsponding fields in pmu_events and event struct.

This patch adds an enum called 'aggr_mode_class' which store all these
aggregation like perchip/percore. It also adds new field 'aggr_mode'
to capture these terms.

Now, if user wants to add any new term, they just need to add it in
the enum defined.

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Clarke <pc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Link: http://lore.kernel.org/lkml/20200907064133.75090-4-kjain@linux.ibm.com


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