perf stat: Use local config arg for scale in create_perf_stat_counter()

perf stat: Use local config arg for scale in create_perf_stat_counter()

Use the local 'scale' member in the 'struct perf_stat_config' argument
instead of the global 'stat_config' variable, to make the function
independent.

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/20180830063252.23729-5-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>