netdevsim: add ipsec hw_features

netdevsim: add ipsec hw_features

Currently, netdevsim only sets dev->features, which makes the ESP features
fixed. For example:

  # ethtool -k eni0np1 | grep esp
  tx-esp-segmentation: on [fixed]
  esp-hw-offload: on [fixed]
  esp-tx-csum-hw-offload: on [fixed]

This patch adds the ESP features to hw_features, allowing them to be
changed manually. For example:

  # ethtool -k eni0np1 | grep esp
  tx-esp-segmentation: on
  esp-hw-offload: on
  esp-tx-csum-hw-offload: on

Suggested-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://patch.msgid.link/20251015083649.54744-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>