selftests/bpf: Export map_update_retriable()

selftests/bpf: Export map_update_retriable()

Export map_update_retriable() to make it usable for other map_test
cases. These cases may only need retry for specific errno, so add
a new callback parameter to let map_update_retriable() decide whether or
not the errno is retriable.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231101032455.3808547-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>