ftrace/x86: Remove function_trace_stop check from graph caller

The graph caller is called by the mcount callers, which already does
the check against the function_trace_stop variable. No reason to
check it again.

Link: http://lkml.kernel.org/r/20120711195745.588538769@goodmis.org



Signed-off-by: Steven Rostedt <rostedt@goodmis.org>