ftrace: annotate core code that should not be traced

Mark with "notrace" functions in core code that should not be
traced.  The "notrace" attribute will prevent gcc from adding
a call to ftrace on the annotated funtions.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>