dt-bindings: soc: Add i.MX8MP media block control DT bindings

The i.MX8MP Media Block Control (MEDIA BLK_CTRL) is a top-level
peripheral providing access to the NoC and ensuring proper power
sequencing of the peripherals within the MEDIAMIX domain. Add DT
bindings for it.

There is already a driver for block controls of other SoCs in the i.MX8M
family, so these bindings will expand upon that.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>