selftests/ftrace: Use top-level available_filter_function

Use top-level available_filter_function if the test case
is running under an instance.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/ftrace/test.d/ftrace/func_traceonoff_triggers.tc

@@ -63,6 +63,10 @@ fi
 
 # powerpc uses .schedule
 func="schedule"
+available_file=available_filter_functions
+if [ -d ../../instances -a -f ../../available_filter_functions ]; then
+   available_file=../../available_filter_functions
+fi
 x=`grep '^\.schedule$' available_filter_functions | wc -l`
 if [ "$x" -eq 1 ]; then
    func=".schedule"