memory_util: boost hashes are size_t

* boost::hash_value returns a size_t
* boost::hash_combine takes a size_t& argument

src/video_core/shader/memory_util.cpp

@@ -66,12 +66,12 @@ ProgramCode GetShaderCode(Tegra::MemoryManager& memory_manager, GPUVAddr gpu_add
 
 u64 GetUniqueIdentifier(Tegra::Engines::ShaderType shader_type, bool is_a, const ProgramCode& code,
                         const ProgramCode& code_b) {
-    u64 unique_identifier = boost::hash_value(code);
+    size_t unique_identifier = boost::hash_value(code);
     if (is_a) {
         // VertexA programs include two programs
         boost::hash_combine(unique_identifier, boost::hash_value(code_b));
     }
-    return unique_identifier;
+    return static_cast<u64>(unique_identifier);
 }
 
 } // namespace VideoCommon::Shader