trace-cmd: Clean up function graph plugin
trace-cmd: Clean up function graph plugin

Because we now have reference counting of records, we do not
need to jump through the hoops of allocating previous records'
data to use it after reading new records.

Remove the hacks from the function graph plugin that does
all this.

Signed-off-by: Steven Rostedt <43232e92d70cc7aa53504ad0397085ee47bad87f@goodmis.org>

bigzz/trace-cmd,bigzz/trace-cmd