interconnect: imx: Add platform driver for imx8mn

Add a platform driver for the i.MX8MN SoC describing bus topology, based
on internal documentation.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Link: https://lore.kernel.org/r/338a5409ce88811ba6c940ba06441db3faa8c187.1586174566.git.leonard.crestez@nxp.com
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>