docs: Add note for LMCache ARM support (#2535)

Co-authored-by: Dmitry Tokarev <dtokarev@nvidia.com>

Author: ZichengMa

components/backends/vllm/LMCache_Integration.md

@@ -11,6 +11,10 @@ This document describes how LMCache is integrated into Dynamo's vLLM backend to
 - **Memory Offloading**: Intelligent KV cache placement across CPU/GPU/storage tiers
 - **Improved Throughput**: Reduced GPU memory pressure enables higher batch sizes
 
+## Platform Support
+
+**Important Note**: LMCache integration currently only supports x86 architecture. ARM64 is not supported at this time.
+
 ## Aggregated Serving