ARM: probes: Use correct action types for MOVW, SEV and WFI

This doesn't correct any bugs when probing these instructions but makes
MOVW slightly faster and makes everything more symmetric with the Thumb
instruction cases.

We can also remove the now redundant PROBES_EMULATE_NONE and
PROBES_SIMULATE_NOP actions.

Signed-off-by: Jon Medhurst <tixy@linaro.org>