Fix missing import during build

Summary: Reported in #11307 that the unordered_map fails to compile in due to https://github.com/pytorch/executorch/blob/main/examples/qualcomm/oss_scripts/llama/runner/rpc_mem.h#L59

Reviewed By: mcr229

Differential Revision: D76278059

Author: cccclai

examples/qualcomm/oss_scripts/llama/runner/rpc_mem.h

@@ -8,6 +8,7 @@
 
 #pragma once
 #include <executorch/examples/qualcomm/oss_scripts/llama/runner/imem_alloc.h>
+#include <unordered_map>
 
 namespace example {
 /**