libbpf: Fix incorrect traversal end type ID when marking BTF_IS_EMBEDDED

When redirecting the split BTF to the vmlinux base BTF, we need to mark
the distilled base struct/union members of split BTF structs/unions in
id_map with BTF_IS_EMBEDDED. This indicates that these types must match
both name and size later. Therefore, we need to traverse the entire
split BTF, which involves traversing type IDs from nr_dist_base_types to
nr_types. However, the current implementation uses an incorrect
traversal end type ID, so let's correct it.

Fixes: 19e00c8 ("libbpf: Split BTF relocation")
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250115100241.4171581-3-pulehui@huaweicloud.com

Author: Pu Lehui

tools/lib/bpf/btf_relocate.c

@@ -212,7 +212,7 @@ static int btf_relocate_map_distilled_base(struct btf_relocate *r)
 	 * need to match both name and size, otherwise embedding the base
 	 * struct/union in the split type is invalid.
 	 */
-	for (id = r->nr_dist_base_types; id < r->nr_split_types; id++) {
+	for (id = r->nr_dist_base_types; id < r->nr_dist_base_types + r->nr_split_types; id++) {
 		err = btf_mark_embedded_composite_type_ids(r, id);
 		if (err)
 			goto done;