tracing: Enable records during the module load

I was debuging some module using "function" and "function_graph"
tracers and noticed, that if you load module after you enabled
tracing, the module's hooks will convert only to NOP instructions.

The attached patch enables modules' hooks if there's function trace
allready on, thus allowing to trace module functions.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20091013203425.896285120@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>