[clang] [CIR] Fix structors for multidimensional arrrays (PR #159820)

[Erich Keane via cfe-commits]

erichkeane wrote:

I don't have a good idea whether this is correct here, and Morris is on PTO the next 2 weeks, and this blocks me on my next OpenACC task.  So hopefully @andykaylor can fixup anything that needs fixing up when he gets back next week, but prompt review would be appreciated!

https://github.com/llvm/llvm-project/pull/159820