dt-bindings: arm: fsl: Add compatible for i.MX8MP audio board (version 2)

dt-bindings: arm: fsl: Add compatible for i.MX8MP audio board (version 2)

Introduce a new DT compatible string for the NXP i.MX8MP audio board
(version 2).

i.MX Audio Board is a configurable and functional audio processing
platform. Integrating a variety of audio input and output interfaces into
the system, the i.MX Audio Board supports HDMI input, HDMI eARC,
S/PDIF I/O, 2-ch ADC line-in, 24-ch DAC line-out and more. Based on these
features, rich audio application cases can be realized.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>