dt-bindings: interconnect: Add Qualcomm MSM8939 DT bindings

The Qualcomm MSM8939 platform has several bus fabrics that could be
controlled and tuned dynamically according to the bandwidth demand.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201204075345.5161-5-jun.nie@linaro.org
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>