perf parse-events: Use strcmp() to compare the PMU name

perf parse-events: Use strcmp() to compare the PMU name

A big uncore event group is split into multiple small groups which only
include the uncore events from the same PMU. This has been supported in
the commit 3cdc5c2cb924a ("perf parse-events: Handle uncore event
aliases in small groups properly").

If the event's PMU name starts to repeat, it must be a new event.
That can be used to distinguish the leader from other members.
But now it only compares the pointer of pmu_name
(leader->pmu_name == evsel->pmu_name).

If we use "perf stat -M LLC_MISSES.PCIE_WRITE -a" on cascadelakex,
the event list is:

  evsel->name					evsel->pmu_name
  ---------------------------------------------------------------
  unc_iio_data_req_of_cpu.mem_write.part0		uncore_iio_4 (as leader)
  unc_iio_data_req_of_cpu.mem_write.part0		uncore_iio_2
  unc_iio_data_req_of_cpu.mem_write.part0		uncore_iio_0
  unc_iio_data_req_of_cpu.mem_write.part0		uncore_iio_5
  unc_iio_data_req_of_cpu.mem_write.part0		uncore_iio_3
  unc_iio_data_req_of_cpu.mem_write.part0		uncore_iio_1
  unc_iio_data_req_of_cpu.mem_write.part1		uncore_iio_4
  ......

For the event "unc_iio_data_req_of_cpu.mem_write.part1" with
"uncore_iio_4", it should be the event from PMU "uncore_iio_4".
It's not a new leader for this PMU.

But if we use "(leader->pmu_name == evsel->pmu_name)", the check
would be failed and the event is stored to leaders[] as a new
PMU leader.

So this patch uses strcmp to compare the PMU name between events.

Fixes: d4953f7ef1a2 ("perf parse-events: Fix 3 use after frees found with clang ASAN")
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200430003618.17002-1-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>