netdev: fix repeated netlink messages in queue dump

netdev: fix repeated netlink messages in queue dump

[ Upstream commit b1f3a2f5a742c1e939a73031bd31b9e557a2d77d ]

The context is supposed to record the next queue to dump,
not last dumped. If the dump doesn't fit we will restart
from the already-dumped queue, duplicating the message.

Before this fix and with the selftest improvements later
in this series we see:

  # ./run_kselftest.sh -t drivers/net:queues.py
  timeout set to 45
  selftests: drivers/net: queues.py
  KTAP version 1
  1..2
  # Check| At /root/ksft-net-drv/drivers/net/./queues.py, line 32, in get_queues:
  # Check|     ksft_eq(queues, expected)
  # Check failed 102 != 100
  # Check| At /root/ksft-net-drv/drivers/net/./queues.py, line 32, in get_queues:
  # Check|     ksft_eq(queues, expected)
  # Check failed 101 != 100
  not ok 1 queues.get_queues
  ok 2 queues.addremove_queues
  # Totals: pass:1 fail:1 xfail:0 xpass:0 skip:0 error:0
  not ok 1 selftests: drivers/net: queues.py # exit=1

With the fix:

  # ./ksft-net-drv/run_kselftest.sh -t drivers/net:queues.py
  timeout set to 45
  selftests: drivers/net: queues.py
  KTAP version 1
  1..2
  ok 1 queues.get_queues
  ok 2 queues.addremove_queues
  # Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0

Fixes: 6b6171db7fc8 ("netdev-genl: Add netlink framework functions for queue")
Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20241213152244.3080955-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>