coresight: Fix all W=1 build warnings

The kernel test robot looks for new warnings in a W=1 build, so fix all
the existing warnings to make it easier to spot new ones when building
locally.

The fixes are for undocumented function arguments and an incorrect doc
style.

Signed-off-by: James Clark <james.clark@arm.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230725140604.1350406-1-james.clark@arm.com