selftests: bpf: centre kernel bpf objects under new subdir "progs"

At the moment, all kernel bpf objects are listed under BPF_OBJ_FILES.
Listing them manually sometimes causing patch conflict when people are
adding new testcases simultaneously.

It is better to centre all the related source files under a subdir
"progs", then auto-generate the object file list.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/progs/test_map_in_map.c

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2018 Facebook */
+#include <stddef.h>
+#include <linux/bpf.h>
+#include <linux/types.h>
+#include "bpf_helpers.h"
+
+struct bpf_map_def SEC("maps") mim_array = {
+	.type = BPF_MAP_TYPE_ARRAY_OF_MAPS,
+	.key_size = sizeof(int),
+	/* must be sizeof(__u32) for map in map */
+	.value_size = sizeof(__u32),
+	.max_entries = 1,
+	.map_flags = 0,
+};
+
+struct bpf_map_def SEC("maps") mim_hash = {
+	.type = BPF_MAP_TYPE_HASH_OF_MAPS,
+	.key_size = sizeof(int),
+	/* must be sizeof(__u32) for map in map */
+	.value_size = sizeof(__u32),
+	.max_entries = 1,
+	.map_flags = 0,
+};
+
+SEC("xdp_mimtest")
+int xdp_mimtest0(struct xdp_md *ctx)
+{
+	int value = 123;
+	int key = 0;
+	void *map;
+
+	map = bpf_map_lookup_elem(&mim_array, &key);
+	if (!map)
+		return XDP_DROP;
+
+	bpf_map_update_elem(map, &key, &value, 0);
+
+	map = bpf_map_lookup_elem(&mim_hash, &key);
+	if (!map)
+		return XDP_DROP;
+
+	bpf_map_update_elem(map, &key, &value, 0);
+
+	return XDP_PASS;
+}
+
+int _version SEC("version") = 1;
+char _license[] SEC("license") = "GPL";