docs: trace: coresight-ect.rst: Fix a build warning

Sphinx wants a line after "..", as otherwise it complains with:

	Documentation/trace/coresight/coresight-ect.rst:2: WARNING: Explicit markup ends without a blank line; unexpected unindent.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200518180242.7916-8-mathieu.poirier@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>