coresight: fix typo in comment in of_coresight.c

Debugfs isn't used for coresight configuration, so the corresponding
comments should be changed.

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>