arm64: dts: imx8mp: add HDMI irqsteer

arm64: dts: imx8mp: add HDMI irqsteer

The HDMI irqsteer is a secondary interrupt controller within the HDMI
subsystem that maps all HDMI peripheral IRQs into a single upstream
IRQ line.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Adam Ford <aford173@gmail.com>
Tested-by: Marek Vasut <marex@denx.de>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Tested-by: Tommaso Merciai <tomm.merciai@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>