selftests: rtnetlink: update netdevsim ipsec output format

selftests: rtnetlink: update netdevsim ipsec output format

After the netdevsim update to use human-readable IP address formats for
IPsec, we can now use the source and destination IPs directly in testing.
Here is the result:
  # ./rtnetlink.sh -t kci_test_ipsec_offload
  PASS: ipsec_offload

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20241010040027.21440-4-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>