ARM: kprobes: Add new versions of emulate_ldr() and emulate_str()

These use the register calling conventions required by the new decoding
table framework for calling simulated instructions.

We rename the old versions of these functions to *_old for now.

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