perf c2c: Free format list entries when releasing c2c hist entries

perf c2c: Free format list entries when releasing c2c hist entries

c2c_hists__init() calls hpp_list__parse() which allocates and registers
format entries on hists->list.  When c2c_he_free() destroys a c2c hist
entry, it deletes the histogram entries and frees the hists container but
never unregisters the format list entries, leaking them.

Call perf_hpp__reset_output_field() before freeing the hists to properly
unregister and free all format entries.

Fixes: f485e33c4543ac31 ("perf c2c report: Add cacheline hists processing")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>