perf stat: Better hybrid support for the NMI watchdog warning

Prior to this patch evlist__has_hybrid would return false if the
processor wasn't hybrid or the evlist didn't contain any core
events. If the only PMU used by events was cpu_core then it would
true even though there are no cpu_atom events. For example:

```
$ perf stat --cputype=cpu_core -e '{cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles}' true

 Performance counter stats for 'true':

     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)
     <not counted>      cpu_core/cycles/                                                        (0.00%)

       0.001981900 seconds time elapsed

       0.002311000 seconds user
       0.000000000 seconds sys
```

This patch changes evlist__has_hybrid to return true only if the
evlist contains events from >1 core PMU. This means the NMI watchdog
warning is shown for the case above.

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Dr. David Alan Gilbert <linux@treblig.org>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Levi Yun <yeoreum.yun@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Weilin Wang <weilin.wang@intel.com>
Link: https://lore.kernel.org/r/20250402201549.4090305-2-irogers@google.com


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