Add link speed support for netdevsim, so users could test different‑speed
NICs. Currently, I am still using max speed 5000. Maybe we should increase
the max speed in the future.

The 2nd patch adds a simple selftest for the speed feature.

Signed-off-by: Hangbin Liu <liuhangbin@kylinos.cn>
---
Hangbin Liu (2):
      netdevsim: add link speed support
      selftests: netdevsim: add speed testing

 drivers/net/netdevsim/dev.c                        |  6 ----
 drivers/net/netdevsim/ethtool.c                    | 30 ++++++++++++++++++++
 drivers/net/netdevsim/netdevsim.h                  |  8 ++++++
 .../selftests/drivers/net/netdevsim/Makefile       |  1 +
 .../drivers/net/netdevsim/ethtool-speed.sh         | 33 ++++++++++++++++++++++
 5 files changed, 72 insertions(+), 6 deletions(-)
---
base-commit: 1bb784eb6e38fd73143f021608e4ef3095d0c0d7
change-id: 20260821-nsim_speed-d61e5c415b02

Best regards,
-- 
Hangbin Liu <liuhangbin@kylinos.cn>