[lldb] Add missing switch case for SveCount in TypeSystemClang::GetEncoding (NFC)

/data/llvm-project/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp:4841:13: error: enumeration value 'SveCount' not handled in switch [-Werror,-Wswitch]
    switch (llvm::cast<clang::BuiltinType>(qual_type)->getKind()) {
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.