selftests/bpf: Enable kptr_xchg_inline test for arm64

Now arm64 bpf jit has enable bpf_jit_supports_ptr_xchg(), so enable
the test for arm64 as well.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20240119102529.99581-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>