eth: gve: add missing netdev locks on reset and shutdown paths

All the misc entry points end up calling into either gve_open()
or gve_close(), they take rtnl_lock today but since the recent
instance locking changes should also take the instance lock.

Found by code inspection and untested.

Fixes: cae03e5b ("net: hold netdev instance lock during queue operations")
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Link: https://patch.msgid.link/20250328164742.1268069-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>