tracing: tprobe-events: Remove mod field from tprobe-event

Remove unneeded 'mod' struct module pointer field from trace_fprobe
because we don't need to save this info.

Link: https://lore.kernel.org/all/174343535351.843280.5868426549023332120.stgit@devnote2/



Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>