perf parse-events: Report BPF errors

Setting the parse_events_error directly doesn't increment num_errors
causing the error message not to be displayed. Use the
parse_events__handle_error function that sets num_errors and handle
multiple errors.

Committer notes:

Ian provided a before/after upon request:

Before:

  $ /tmp/perf/perf record -e /tmp/perf/util/parse-events.o
  Run 'perf list' for a list of valid events

  Usage: perf record [<options>] [<command>]
     or: perf record [<options>] -- <command> [<options>]

     -e, --event <event>   event selector. use 'perf list' to list available event

After:

  $ /tmp/perf/perf record -e /tmp/perf/util/parse-events.o
  event syntax error: '/tmp/perf/util/parse-events.o'
                      \___ Failed to load /tmp/perf/util/parse-events.o: BPF object format invalid

  (add -v to see detail)
  Run 'perf list' for a list of valid events

  Usage: perf record [<options>] [<command>]
     or: perf record [<options>] -- <command> [<options>]

     -e, --event <event>   event selector. use 'perf list' to list available events

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: bpf@vger.kernel.org
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@chromium.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: netdev@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Yonghong Song <yhs@fb.com>
Link: http://lore.kernel.org/lkml/20200707211449.3868944-1-irogers@google.com


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