dt-bindings: arm: imx: add imx8mq nitrogen support

The Nitrogen8M is an ARM based single board computer (SBC)
designed to leverage the full capabilities of NXP’s i.MX8M
Quad processor.

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
[Dafna: porting vendor's code to mainline]
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>