coresight: etm4x: Do not hardcode IOMEM access for register restore

When we restore the register state for ETM4x, while coming back
from CPU idle, we hardcode IOMEM access. This is wrong and could
blow up for an ETM with system instructions access (and for ETE).

Fixes: f5bd5236 ("coresight: etm4x: Convert all register accesses")
Reported-by: Yabin Cui <yabinc@google.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Yabin Cui <yabinc@google.com>
Link: https://lore.kernel.org/r/20240412142702.2882478-2-suzuki.poulose@arm.com