arm64: dts: ti: k3-am625-beagleplay: Add HDMI support

arm64: dts: ti: k3-am625-beagleplay: Add HDMI support

The DSS outputs DPI signals via its second video port (VP2). The DPI
output from DSS is 24 bits (RGB888) and is forwarded to an HDMI
transmitter (ITE-IT66121) on the BeaglePlay platform. For audio output,
BeaglePlay uses mcasp1.

Add pinmux info for DSS DPI signals.

Further, add support for HDMI audio and video output.

Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
Link: https://lore.kernel.org/r/20230809084559.17322-6-a-bhatia1@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>