perf c2c: Add local variables for output metrics

perf c2c: Add local variables for output metrics

This patch adds several local variables:

  "cl_output": pointer for outputting single cache line metrics;
  "output_str": pointer for outputting cache line metrics;
  "sort_str": pointer to the sorting metrics.

This can improve readability for the code and it's more flexible when
later extend to different strings for the output metrics.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210114154646.209024-7-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>