amd-xgbe: add ARP offload and RSS self-tests

This series adds ARP offload support and ethtool self-tests for the AMD XGBE 10 Gigabit Ethernet driver.

Patch 1 is a build fix for randconfig coverage.

Patch 2 adds hardware ARP offload functionality that allows the MAC to automatically respond to ARP requests without CPU intervention, reducing system latency and power consumption during suspend/resume and normal operation.

Patches 3 and 4 add ethtool self-tests for ARP offload and RSS functionality respectively, allowing users to verify these hardware features are working correctly via 'ethtool -t <interface>'.

The tests are integrated into the existing XGBE self-test framework that already includes MAC loopback, PHY loopback, split header, and jumbo frame tests.

Test results example:

  $ ethtool -t eth0
  The test result is PASS
  The test extra info:
  MAC Loopback       0
  PHY Loopback       0
  Split Header       0
  Jumbo Frame        0
  ARP Offload        0
  RSS                0

Changes since v2:
- Fix warnings about line length
- Use kfree_skb() instead of kfree() for skb cleanup in self-tests
- CC maintainer for patch 1

Changes since v1:
- Resubmitting to net-next as this was mistakenly sent to net previously.
- Fix INET=n build breakage reported by kernel test robot
- Ensure ARP self-test cleanup is safe on all error paths (no dangling packet handler).
- Use link-local IPs for self-tests to avoid interfering with real network configuration.

Raju Rangoju (4):
amd-xgbe: do not select NET_SELFTESTS when INET is disabled
amd-xgbe: add hardware ARP offload support
amd-xgbe: add ARP offload ethtool self-test
amd-xgbe: add RSS ethtool self-test

 drivers/net/ethernet/amd/Kconfig              |   2 +-
 drivers/net/ethernet/amd/xgbe/xgbe-common.h   |   3 +
 drivers/net/ethernet/amd/xgbe/xgbe-dev.c      |  24 +++
 drivers/net/ethernet/amd/xgbe/xgbe-selftest.c | 154 +++++++++++++++++-
 drivers/net/ethernet/amd/xgbe/xgbe.h          |   4 +
 include/net/selftests.h                       |   1 +
 6 files changed, 186 insertions(+), 2 deletions(-)

2.34.1