selftests: hid: enforce new attach API

Now that the new API for hid_bpf_attach_prog() is in place, ensure we
get an fd when calling this function. And remove the fallback code.

Signed-off-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

tools/testing/selftests/hid/hid_bpf.c

···
 	LOAD_PROGRAMS(progs);
 
 	link = self->hid_links[0];
-	/* we might not be using the new code path where hid_bpf_attach_prog()
-	 * returns a link.
-	 */
-	if (!link)
-		link = bpf_program__fd(self->skel->progs.hid_first_event);
+	ASSERT_GT(link, 0) TH_LOG("HID-BPF link not created");
 
 	/* inject one event */
 	buf[0] = 1;