This patch restores the ability to set msglvl through ethtool.
The issue was introduced by:
commit 849c4542

CC: Joe Perches <joe@perches.com>
Reported-by: NJoe Perches <joe@perches.com>
Signed-off-by: NEmil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>