The 'freelist' member was introduced to 'struct dyn_ftrace' in commit ee000b7f9fe429d2470c674ccec8d344f6789e0d (tracing: use union for
multi-usages field), but the use of this member was later removed in 3208230983a0ee3d95be22d463257e530c684956 (ftrace: Remove usage of
"freed" records). Remove also the 'freelist' member now.