rcutorture: add nolibc init support for mips, ppc and rv64

Use nolibc for all support architectures.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>