coresight: Unify bus unregistration via coresight_unregister()

coresight: Unify bus unregistration via coresight_unregister()

Once a device is successfully registered, set the "registered" flag to
true.  After that point, all failures jump to the out_unlock label to
unwind the flow via coresight_unregister().

Since failure handling is unified, the comment about resource release
for the etm_perf_add_symlink_sink() failure is no need, remove it.

Signed-off-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20260209-arm_coresight_refactor_dev_register-v4-8-62d6042f76f7@arm.com