net/mlx5e: IPoIB, Fix driver name retrieved by ethtool

Printing an enhanced IPoIB device information using
"ethtool -i DEVNAME", prints the low level driver name: mlx5_core.
This commit changes the name to mlx5_core [ib_ipoib], to include the
ipoib device driver infromation.

Fixes: 076b0936 ("net/mlx5e: IPoIB, Add ethtool support")
Signed-off-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>