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

In the Linux kernel, the following vulnerability has been resolved:

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.