[AIX][XCOFF] add symbol priority for the llvm-objdump -D -symbol-description

SUMMARY:
when there are two symbol has the same address. llvm-objdump -D -symbol-description will select symbol based on the following rule:

1. using Label first if there is a Label symbol.
2. If there is not Label, using a symbol which has Storage Mapping class.
3. if more than one symbol has storage mapping class, put the TC0 has the low priority, for other storage mapping class , compare based on the value.

Reviewers: James Henderson ,hubert.reinterpretcast,

Differential Revision: https://reviews.llvm.org/D78387