coresight: remove the unnecessary configuration coresight-default-sink

The coresight-default-sink configuration option has been
removed from the framework. As such remove it from DT and bindings.

Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>