selftests: hid: prepare tests for HID_BPF API change

We plan on changing the return value of hid_bpf_attach_prog().
Instead of returning an error code, it will return an fd to a bpf_link.
This bpf_link is responsible for the binding between the bpf program and
the hid device.

Add a fallback mechanism to not break bisections by pinning the program
when we run this test against the non changed kernel.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>