ethtool: stats: Fix a copy-paste error

data->ctrl_stats should be memset with correct size.

Fixes: bfad2b97 ("ethtool: add interface to read standard MAC Ctrl stats")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>