[SE] Include absl/memory/memory.h

[SaveTheRbtz]

Otherwise our build environment fails to build it with:

external/org_tensorflow/tensorflow/stream_executor/host/host_platform.cc: In member function 'virtual stream_executor::port::StatusOr<std::unique_ptr<stream_executor::StreamExecutor> > stream_executor::host::HostPlatform::GetUncachedExecutor(const stream_executor::StreamExecutorConfig&)':
external/org_tensorflow/tensorflow/stream_executor/host/host_platform.cc:73:25: error: 'make_unique' is not a member of 'absl'
   auto executor = absl::make_unique<StreamExecutor>(
                         ^~~~~~~~~~~