perf tools: Fix event's PMU name parsing

perf tools: Fix event's PMU name parsing

Jin Yao reported parser error for software event:

  # perf stat -e software/r1a/ -a -- sleep 1
  event syntax error: 'software/r1a/'
                       \___ parser error

This happens after commit 8c3b1ba0e7ea9a80 ("drm/i915/gt: Track the
overall awake/busy time"), where new software-gt-awake-time event's
non-pmu-event-style makes event parser conflict with software PMU.

If we allow PE_PMU_EVENT_PRE to be parsed as PMU name, we fix the
conflict and the following character '/' for PMU or '-' for
non-pmu-event-style event allows parser to decide what even is
specified.

Fixes: 8c3b1ba0e7ea9a80 ("drm/i915/gt: Track the overall awake/busy time")
Reported-by: Jin Yao <yao.jin@linux.intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210301122315.63471-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>