libperf: Adopt perf_counts_values__scale() from tools/perf/util

Move perf_counts_values__scale() from tools/perf/util to tools/lib/perf
so that it can be used with libperf.

Committer notes:

As noted by Jiri, use __s8 instead of s8 on the exported function.

Signed-off-by: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211109085831.3770594-2-nakamura.shun@fujitsu.com


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