perf hist: Don't set hpp_fmt_value for members in --no-group

perf hist: Don't set hpp_fmt_value for members in --no-group

Perf crashes as below when applying --no-group

  # perf record -e "{cache-misses,branches"} -b sleep 1
  # perf report --stdio --no-group
  free(): invalid next size (fast)
  Aborted (core dumped)
  #

In the __hpp__fmt(), only 1 hpp_fmt_value is allocated for the current
event when --no-group is applied.

However, the current implementation tries to assign the hists from all
members to the hpp_fmt_value, which exceeds the allocated memory.

Fixes: 8f6071a3dce40e69 ("perf hist: Simplify __hpp_fmt() using hpp_fmt_data")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240820183202.3174323-1-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>