[mlir][sparse] Moved _mlir_ciface_newSparseTensor closer to its macros

This is a followup to D125431, to keep from confusing the machinery that generates diffs (since combining these two changes into one would obfuscate the changes actually made in the previous differential).

Depends On D125431

Reviewed By: aartbik

Differential Revision: https://reviews.llvm.org/D125432