tracing: Have function_graph use trace_seq_has_overflowed()

Instead of doing individual checks all over the place that makes the code
very messy. Just check trace_seq_has_overflowed() at the end or in
strategic places.

This makes the code much cleaner and also helps with getting closer
to removing the return values of trace_seq_printf() and friends.

Link: http://lkml.kernel.org/r/20141114011410.987913836@goodmis.org
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --cc kernel/trace/trace.h
Simple merge

diff --cc kernel/trace/trace_functions_graph.c
Simple merge