ARM: kprobes: Framework for instruction set test cases

On ARM we have to simulate/emulate CPU instructions in order to
singlestep them. This patch adds a framework which can be used to
construct test cases for different instruction forms. It is described in
detail in the in-source comments of kprobes-test.c

Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>