81-hid-bpf.rules: always set --bpfdir

The code currently aborts if --bpfdir is not provided and if DEFAULT_BPF_DIRS doesn't exist. This is because if this directory doesn't exist, we can not really load anything from it so we better bail out.

In the general meson install case, this is fine because meson knows about the actual $PREFIX used to install the target.

But in the make_release.sh case, meson is given a temporary directory as a prefix and thus has a poisoned DEFAULT_BPF_DIRS.

To ensure we always use the installed data, enfore --bpfdir in the udev rule so we don't get any surprises.