ftrace: Avoid recording mcount on .init sections directly

The init and exit sections should not be traced and adding a call to
mcount to them is a waste of text and instruction cache. Have the
macro section attributes include notrace to ignore these functions
for tracing from the build.

Link: http://lkml.kernel.org/r/20110421023738.953028219@goodmis.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>