coresight: Drop atomics in connection refcounts

These belong to the device being enabled or disabled and are only ever
used inside the device's spinlock. Remove the atomics to not imply that
there are any other concurrent accesses.

If atomics were necessary I don't think they would have been enough
anyway. There would be nothing to prevent an enable or disable running
concurrently if not for the spinlock.

Signed-off-by: James Clark <james.clark@linaro.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20241128121414.2425119-1-james.clark@linaro.org