PRelu Int16x8 Ref C support

[rameshkunasi]

@tensorflow/micro

Add PReLu int16x8 support in reference C

bug=fixes #3168

[veblush]

Thanks for this PR! This is looking good. I just have a couple of minor comments.

[veblush]

Thank you for the PR! LGTM.

[mergify]

This pull request has been removed from the queue for the following reason: pull request dequeued.

Pull request #3191 has been dequeued. The pull request could not be merged. This could be related to an activated branch protection or ruleset rule that prevents us from merging. (details: 19 of 20 required status checks have not succeeded: 1 expected.).

You should look at the reason for the failure and decide if the pull request needs to be fixed or if you want to requeue it.
If you do update this pull request, it will automatically be requeued once the queue conditions match again.
If you think this was a flaky issue instead, you can requeue the pull request, without updating it, by posting a @mergifyio requeue comment.

[veblush]

Running the Mergify test again appears to resolve the issue, which suggests it might have a bug.