tracing: probe-events: Add comments about entry data storing code

Add comments about entry data storing code to __store_entry_arg() and
traceprobe_get_entry_data_size(). These are a bit complicated because of
building the entry data storing code and scanning it.

This just add comments, no behavior change.

Link: https://lore.kernel.org/all/174061715004.501424.333819546601401102.stgit@devnote2/



Reported-by: Steven Rostedt <rostedt@goodmis.org>
Closes: https://lore.kernel.org/all/20250226102223.586d7119@gandalf.local.home/


Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>