libbpf: Add SEC name for xdp programs attached to CPUMAP

As for DEVMAP, support SEC("xdp_cpumap/") as a short cut for loading
the program with type BPF_PROG_TYPE_XDP and expected attach type
BPF_XDP_CPUMAP.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/33174c41993a6d860d9c7c1f280a2477ee39ed11.1594734381.git.lorenzo@kernel.org

tools/lib/bpf/libbpf.c

@@ -6912,6 +6912,8 @@ static const struct bpf_sec_def section_defs[] = {
 		.attach_fn = attach_iter),
 	BPF_EAPROG_SEC("xdp_devmap/",		BPF_PROG_TYPE_XDP,
 						BPF_XDP_DEVMAP),
+	BPF_EAPROG_SEC("xdp_cpumap/",		BPF_PROG_TYPE_XDP,
+						BPF_XDP_CPUMAP),
 	BPF_PROG_SEC("xdp",			BPF_PROG_TYPE_XDP),
 	BPF_PROG_SEC("perf_event",		BPF_PROG_TYPE_PERF_EVENT),
 	BPF_PROG_SEC("lwt_in",			BPF_PROG_TYPE_LWT_IN),