Now that we find bpf_rb_root and bpf_rb_node in structs, let's give args
that contain those types special classification and properly handle
these types when checking kfunc args.

"Properly handling" these types largely requires generalizing similar
handling for bpf_list_{head,node}, with little new logic added in this
patch.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230214004017.2534011-4-davemarchevsky@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>