GPU: clean up GPU index detection code

src/detection/gpu/gpu_amd.c

@@ -65,5 +65,8 @@ const char* ffDetectAmdGpuInfo(const FFGpuDriverCondition* cond, FFGpuDriverResu
     if (result.type)
         *result.type = device->isAPU ? FF_GPU_TYPE_INTEGRATED : FF_GPU_TYPE_DISCRETE;
 
+    if (result.index)
+        *result.type = (uint32_t) device->adlAdapterIndex;
+
     return NULL;
 }