tracing: Exit with error if a weak function is used in recordmcount.pl

If a weak function is used as a relocation reference for mcount callers
and that function is overridden, it will cause ftrace to fail at run time.

The current code should prevent a weak function from being used, but if
one is, the code should exit with an error to fail at compile time.

Signed-off-by: Li Hong <lihong.hi@gmail.com>
LKML-Reference: <20091028050743.GH30758@uhli>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>