MC: Stop using MCSymbolData::getSymbol() in WinCOFF, NFC

Move APIs over from `MCSymbolData` to `MCSymbol`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237826 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed