selftests/bpf: Add a test where map key_type_id with decl_tag type

Add two selftests where map creation key/value type_id's are
decl_tags. Without previous patch, kernel warnings will
appear similar to the one in the previous patch. With the previous
patch, both kernel warnings are silenced.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230530205034.266643-1-yhs@fb.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/prog_tests/btf.c

@@ -3990,6 +3990,46 @@ static struct btf_raw_test raw_tests[] = {
 	.btf_load_err = true,
 	.err_str = "Invalid arg#1",
 },
+{
+	.descr = "decl_tag test #18, decl_tag as the map key type",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_STRUCT_ENC(0, 2, 8),			/* [2] */
+		BTF_MEMBER_ENC(NAME_TBD, 1, 0),
+		BTF_MEMBER_ENC(NAME_TBD, 1, 32),
+		BTF_DECL_TAG_ENC(NAME_TBD, 2, -1),		/* [3] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0m1\0m2\0tag"),
+	.map_type = BPF_MAP_TYPE_HASH,
+	.map_name = "tag_type_check_btf",
+	.key_size = 8,
+	.value_size = 4,
+	.key_type_id = 3,
+	.value_type_id = 1,
+	.max_entries = 1,
+	.map_create_err = true,
+},
+{
+	.descr = "decl_tag test #19, decl_tag as the map value type",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_STRUCT_ENC(0, 2, 8),			/* [2] */
+		BTF_MEMBER_ENC(NAME_TBD, 1, 0),
+		BTF_MEMBER_ENC(NAME_TBD, 1, 32),
+		BTF_DECL_TAG_ENC(NAME_TBD, 2, -1),		/* [3] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0m1\0m2\0tag"),
+	.map_type = BPF_MAP_TYPE_HASH,
+	.map_name = "tag_type_check_btf",
+	.key_size = 4,
+	.value_size = 8,
+	.key_type_id = 1,
+	.value_type_id = 3,
+	.max_entries = 1,
+	.map_create_err = true,
+},
 {
 	.descr = "type_tag test #1",
 	.raw_types = {