selftests/bpf: Fix casting error when cross-compiling test_verifier for 32-bit platforms

When cross-compiling test_verifier for 32-bit platforms, the casting error is shown below:

test_verifier.c:1263:27: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
 1263 |  info.xlated_prog_insns = (__u64)*buf;
      |                           ^
cc1: all warnings being treated as errors

Fix it by adding zero-extension for it.

Fixes: 933ff531 ("selftests/bpf: specify expected instructions in test_verifier tests")
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221108121945.4104644-1-pulehui@huaweicloud.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/test_verifier.c

@@ -1260,7 +1260,7 @@ static int get_xlated_program(int fd_prog, struct bpf_insn **buf, int *cnt)
 
 	bzero(&info, sizeof(info));
 	info.xlated_prog_len = xlated_prog_len;
-	info.xlated_prog_insns = (__u64)*buf;
+	info.xlated_prog_insns = (__u64)(unsigned long)*buf;
 	if (bpf_obj_get_info_by_fd(fd_prog, &info, &info_len)) {
 		perror("second bpf_obj_get_info_by_fd failed");
 		goto out_free_buf;