tf-lite CMake: add headers into sources to correctly install them
Hi @terryheo Can you please review this PR ? Thank you!
The headers delegate.h and delegate_options.h were missing when tensorflow lite was installed with the GPU delegates using CMake.

This PR just add these 2 files into TFLITE_DELEGATES_GPU_SRCS variable and it fixes the issue. It works because TFLITE_DELEGATES_GPU_SRCS is used to create _ALL_TFLITE_SRCS which is used to have _ALL_TFLITE_HDRS and then all headers from this variables are installed.

Previous PR discarded because of CLA : https://github.com/tensorflow/tensorflow/pull/63016