selftests/ftrace: add mips support for kprobe args syntax tests

This is the mips variant of commit <3990b5ba> ("selftests/ftrace:
Add s390 support for kprobe args tests").

Signed-off-by: Ze Zhang <zhangze@loongson.cn>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>