selftests/uprobes: Add a basic uprobe testcase

Add a basic uprobe testcase which checks whether add/remove/trace
operations works on /bin/sh.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>