Fix #11785 by making reifyKind = reifyType

Summary:
This ties up the last loose end in Template Haskell's separate
code paths for types and kinds. By making `reifyKind = reifyType` in
`TcSplice`, types and kinds are now treated on equal terms in TH.

This is itself a small patch, but most of the heavy lifting to make this
possible was done in ad7b9452.

Test Plan: ./validate

Reviewers: goldfire, austin, bgamari

Reviewed By: goldfire

Subscribers: rwbarton, thomie

GHC Trac Issues: #11785

Differential Revision: https://phabricator.haskell.org/D3854