[llvm] [flang-rt] Fix TypeCategory for quad-precision COMPLEX (PR #168090)

[Carlos Seo via llvm-commits]

ceseo wrote:

> You could add a test like this using a `fir.box<cpmlx.complex<f128>>` type instead of the derived type. The resulting descriptor structure should contain the type code value.

My question was more in the lines of where in the directory structure is more adequate. Although the fix is in flang-rt, this is technically lowering. Maybe `flang/test/Lower`?

https://github.com/llvm/llvm-project/pull/168090