[clang] [OpenACC] Fix uses of getBaseOriginalType when we really want elt type. (PR #162880)

[Erich Keane via cfe-commits]

erichkeane wrote:

Still going to auto-merge, but found a few things I can use as a test, so stopping it since validation will be finished before i get my tests up :) 

https://github.com/llvm/llvm-project/pull/162880