[XCOFF][AIX] Use TE storage mapping class when large code model is enabled

Summary:
Use TE SMC instead of TC SMC in large code model mode,
so that large code model TOC entries could get placed after all
the small code model TOC entries, which reduces the chance of TOC overflow.

Reviewed By: Xiangling_L

Differential Revision: https://reviews.llvm.org/D85455