net/mlx5e: IPoIB, Add ethtool support

Add support for the following:
	"ethtool -S" (statistics).
	"ethtool -i" (driver info).
	"ethtool -g/G" (rings parameters).
	"ethtool -l/L" (channels parameters).
	"ethtool -c/C" (coalesce options).

Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>