MC: Use MCSymbol in MCAsmLayout::getSymbolOffset(), NFC

Continue to canonicalize on MCSymbol instead of MCSymbolData when both
are needed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237749 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed