perf stat: Fix metrics with --no-merge

Since Fixes: 8c5421c0 ("perf pmu: Display pmu name when printing
unmerged events in stat") using --no-merge adds the PMU name to the
evsel name.

This breaks the metric value lookup because the parser doesn't know
about this.

Remove the extra postfixes for the metric evaluation.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Agustin Vega-Frias <agustinv@codeaurora.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Fixes: 8c5421c0 ("perf pmu: Display pmu name when printing unmerged events in stat")
Link: http://lkml.kernel.org/r/20190624193711.35241-5-andi@firstfloor.org


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