coresight: Use coresight device names for sinks in PMU attribute

Move to using the coresight device name instead of the parent
device name for SINK attribute for PMU.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>