arm64: dts: juno: refactor CoreSight support on Juno r0

Currently the Coresight components are supported only on Juno r0
variant. In preparation to add support to Juno r1/r2 variants, this
patch refactors the existing coresight device nodes so that r1/r2
support can be added easily.

It also cleans up some of the device node names which were previously
named so as they were confused as the labels rather than the node names.

Reviewed-and-tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>