coresight: Fixes coresight DT parse to get correct output port ID.

Corrected to get the port numbering to allow programmable replicator driver
to operate correctly.

By convention, CoreSight devices number ports, not endpoints in
the .dts files:-

port {
     reg<N>
     endpoint {
     }
}

Existing code read endpoint number - always 0x0, rather than the correct
port number.

Signed-off-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>