selftests/ftrace: Convert tracer tests to use 'requires' to specify program dependency

Now that we have a good way to specify dependency of tests on programs,
convert some of the tracer tests to use this method for specifying
dependency on 'chrt'.

Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>