bpftool: Remove unused struct btf_attach_point

After commit 2828d0d7 ("bpftool: Switch to libbpf's hashmap for
programs/maps in BTF listing"), struct btf_attach_point is not used
anymore and can be removed as well.
Signed-off-by: Yuan Can <yuancan@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220928090440.79637-2-yuancan@huawei.com

tools/bpf/bpftool/btf.c

@@ -43,11 +43,6 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_ENUM64]	= "ENUM64",
 };
 
-struct btf_attach_point {
-	__u32 obj_id;
-	__u32 btf_id;
-};
-
 static const char *btf_int_enc_str(__u8 encoding)
 {
 	switch (encoding) {