fix(config): structure LMCache backend metadata

Author: cquil11

configs/amd-master.yaml

@@ -561,7 +561,7 @@ kimik2.7-fp4-mi355x-vllm-agentic:
     - dram-utilization: 0.80
       search-space:
       - { tp: 4, kv-offloading: none, conc-list: [1, 4, 8] }
-      - { tp: 4, kv-offloading: dram, kv-offload-backend: lmcache, conc-list: [16, 32] }
+      - { tp: 4, kv-offloading: dram, kv-offload-backend: { name: lmcache, version: "aaf7c0d3" }, conc-list: [16, 32] }
 
 
 kimik2.5-fp4-mi355x-atom: