ARM: kprobes: Decode 32-bit Thumb load/store dual and load/store exclusive instructions

We reject probing of load/store exclusive instructions because any
emulation routine could never succeed in gaining exclusive access as the
exception framework clears the exclusivity monitor when a probes
breakpoint is hit.

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