net/mlx5e: Add error flow for ethtool -X command

Prior to this patch, ethtool -X fail but the user receives a success
status. Try to roll-back when failing and return success status
accordingly.

Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>