perf jevents: Use name for special find value (PMU_EVENTS__NOT_FOUND)

perf jevents: Use name for special find value (PMU_EVENTS__NOT_FOUND)

-1000 was used as a special value added in Commit 3d5045492ab2 ("perf
pmu-events: Add pmu_events_table__find_event()") to show that 1 table
lacked a PMU/event but that didn't terminate the search in other
tables.

Add a new constant PMU_EVENTS__NOT_FOUND for this value and use it.

Reviewed-by: John Garry <john.g.garry@oracle.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: Ingo Molnar <mingo@redhat.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oliver Sang <oliver.sang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Philip Li <philip.li@intel.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Weilin Wang <weilin.wang@intel.com>
Cc: Xu Yang <xu.yang_2@nxp.com>
Link: https://lore.kernel.org/r/20240730191744.3097329-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>