coresight: etm4x: Do not save/restore Data trace control registers

ETM4x doesn't support Data trace on A class CPUs. As such do not access the
Data trace control registers during CPU idle. This could cause problems for
ETE. While at it, remove all references to the Data trace control registers.

Fixes: f188b5e7 ("coresight: etm4x: Save/restore state across CPU low power states")
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/20240412142702.2882478-3-suzuki.poulose@arm.com