default or selected kernelversion does not have config value CONFIG_DRM_ZYNQMP_DPSUB_AUDIO.
Result is shown for kernelversion 6.6.78

ZynqMP DisplayPort Audio Support

configname: CONFIG_DRM_ZYNQMP_DPSUB_AUDIO

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)
└─>ZynqMP DisplayPort Audio Support
In linux kernel since version 6.6.78 (release Date: 2025-02-17)  
Choose this option to enable DisplayPort audio support in the ZynqMP
DisplayPort driver.