CVE-2025-22099 drm: xlnx: zynqmp_dpsub: Add NULL check in zynqmp_audio_init

In the Linux kernel, the following vulnerability has been resolved: drm: xlnx: zynqmpdpsub: Add NULL check in zynqmpaudioinit devmkasprintf calls can return null pointers on failure. But some return values were not checked in zynqmpaudioinit. Add NULL check in zynqmpaudioinit, avoid referencing...