[lldb] Fix enumeration value 'RvvInt32m1x2' not handled in switch (NFC)

/data/llvm-project/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp:4851:13: error: enumeration value 'RvvInt32m1x2' not handled in switch [-Werror,-Wswitch]
    switch (llvm::cast<clang::BuiltinType>(qual_type)->getKind()) {
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
ninja: build stopped: subcommand failed.