coresight: adding the LINKSINK block as a sink type

>From the TMC TRM, the ETF can be configured as buffer mode, so ETF can
be a sink type.

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