Documentation: HID: amend HID-BPF for struct_ops

Now that we are using struct_ops, the docs need to be changed.

Link: https://lore.kernel.org/r/20240608-hid_bpf_struct_ops-v3-10-6ac6ade58329@kernel.org


Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>