net: dsa: remove redundant netdev_lock_ops() from conduit ethtool ops

net: dsa: remove redundant netdev_lock_ops() from conduit ethtool ops

DSA replaces the conduit (master) device's ethtool_ops with its own
wrappers that aggregate stats from both the conduit and DSA switch
ports. Taking the lock again inside the DSA wrappers causes a deadlock.

Stumbled upon this when booting qemu with fbnic and CONFIG_NET_DSA_LOOP=y
(which looks like some kind of testing device that auto-populates the ports
of eth0). `ethtool -i` is enough to deadlock. This means we have basically zero
coverage for DSA stuff with real ops locked devs.

Remove the redundant netdev_lock_ops()/netdev_unlock_ops() calls from
the DSA conduit ethtool wrappers.

Fixes: 2bcf4772e45a ("net: ethtool: try to protect all callback with netdev instance lock")
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20260414231035.1917035-1-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>