coresight: Make new csdev_access offsets unsigned

New csdev_access functions were added as part of the previous
refactor. In order to make them more consistent with the
existing ones, change any signed offset types to be unsigned.

Now that they are unsigned, stop using hi_off = -1 to signify
a single 32bit access. Instead just call the existing 32bit
accessors. This is also applied to other parts of the codebase,
and the coresight_{read,write}_reg_pair() functions can be
deleted.

Signed-off-by: James Clark <james.clark@arm.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Link: https://lore.kernel.org/r/20220830172614.340962-6-james.clark@arm.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>