Move SystemZ-specific MCSymbolRefExpr::VariantKind to SystemZMCExpr::Specifier
Similar to previous migration done for other targets (PowerPC, X86, ARM,
etc). Switch from the confusing VariantKind to Specifier, which aligns
with Arm and IBM AIX's documentation.
In addition, rename *MCExpr::getKind, which confusingly shadows the base class getKind.
In the future, relocation specifiers should be encoded as part of
SystemZMCExpr instead of MCSymbolRefExpr.
llvm-project
b19b6d9f - Move SystemZ-specific MCSymbolRefExpr::VariantKind to SystemZMCExpr::Specifier
