Always link kernels_experimental c api
@jianyizh,
Can you please sign CLA. Thank you! > @jianyizh, Can you please sign CLA. Thank you!

The "cla/google" CI is passed, I'm covered by Corporate CLA. Do I need sign Individual CLA? @penpornk Can you help review this pr? It's just one line of code. Follow internal process and use this pr https://github.com/tensorflow/tensorflow/pull/60786 Thank you for the PR and sorry for the delay! I have approved https://github.com/tensorflow/tensorflow/pull/60786.
[PluggableDevice](https://github.com/tensorflow/community/blob/master/rfcs/20200624-pluggable-device-for-tensorflow.md) architecture relies on C APIs to communicate with the TensorFlow binary. To support pluggable device for tensorflow serving (https://github.com/tensorflow/serving/pull/2144), we need add always_link=1 for `kernels_experimental`.