perf tools: Fix comment for sort__* compare functions
In commit
2f15bd8c6c6e ("perf tools: Fix "Command" sort_entry's cmp and
collapse function") we switched from pointer to string comparison.
But failed to remove related comments. Removing them and adding another
one to warn before pointer comparison in here.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180206181813.10943-18-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>