coresight-funnel: add CoreSight Funnel driver

This driver manages CoreSight Funnel which acts as a link.
Funnels have multiple input ports (typically 8) each of which
represents an input trace data stream. These multiple input trace
data streams are interleaved into a single output stream coming
out of the Funnel.

Signed-off-by: Pratik Patel <pratikp@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>