dt-bindings: interconnect: Add bindings for imx8m noc

dt-bindings: interconnect: Add bindings for imx8m noc

Add initial dt bindings for the interconnects inside i.MX chips.
Multiple external IPs are involved but SOC integration means the
software controllable interfaces are very similar.

Main NOC node acts as interconnect provider if #interconnect-cells is
present. Currently there is a single imx interconnect provider for the
whole SOC.

Other pieces of scalable interconnects can be present, each with their
own OPP table.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/8b341d91e9aee679ae69feb22a2c842b2aeb2137.1586174566.git.leonard.crestez@nxp.com
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>