selftests/bpf: Update the demo file_read_pattern to run on libbpf 1.0+

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8O4U8
CVE: NA

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Some APIs are removed and some APIs are changed from libbpf 1.0 or
later. The purpose of this patch is to enable the demo to run
successfully on libbpf 1.0+.

For details about API changes, see the following link:
  https://github.com/libbpf/libbpf/wiki/Libbpf:-the-road-to-v1.0
  https://github.com/libbpf/libbpf/wiki/Libbpf-1.0-migration-guide



Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>