perf stat: Add 'struct perf_tool' argument to perf_stat_synthesize_config()

perf stat: Add 'struct perf_tool' argument to perf_stat_synthesize_config()

So that we can use the function outside the 'perf stat' command with standard
synthesize functions, that take 'struct perf_tool *' argument.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180830063252.23729-12-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>