wil6210: get rid of begin() and complete() ethtool_ops

The wil6210 driver locks a mutex in begin() ethtool_ops callback and
unlocks it in complete() so that all ethtool requests are serialized. This
is not going to work correctly with netlink interface; e.g. when ioctl
triggers a netlink notification, netlink code would call begin() again
while the mutex taken by ioctl code is still held by the same task.

Let's get rid of the begin() and complete() callbacks and move the mutex
locking into the remaining ethtool_ops handlers except get_drvinfo which
only copies strings that are not changing so that there is no need for
serialization.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>