ASoC: dt-bindings: covert mxs-audio-sgtl5000.txt to yaml format

Convert mxs-audio-sgtl5000.txt to yaml format.

Additional changes:
- Add compatible string:
    bluegiga,apx4devkit-sgtl5000
    denx,m28evk-sgtl5000
    fsl,imx28-mbmx28lc-sgtl500
- Remove audio-routing from required list.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: "Rob Herring (Arm)" <robh@kernel.org>
Link: https://patch.msgid.link/20250528165755.692264-1-Frank.Li@nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>