selftests: rtnetlink: correct xfrm policy rule in kci_test_ipsec_offload

selftests: rtnetlink: correct xfrm policy rule in kci_test_ipsec_offload

When testing in kci_test_ipsec_offload, srcip is configured as $dstip,
it should add xfrm policy rule in instead of out.
The test result of this patch is as follows:
PASS: ipsec_offload

Fixes: 01ccdbdfa370 ("selftests: rtnetlink: add ipsec offload API test")
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Acked-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20221201082246.14131-1-shaozhengchao@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>