net: dsa: Remove redundant phy_attach()

dsa_slave_phy_setup() finds the phy for the port via device tree and
using of_phy_connect(), or it uses the fall back of taking a phy from
the switch internal mdio bus and calling phy_connect_direct(). Either
way, if a phy is found, phy_attach_direct() is called to attach the
phy to the slave device.

In dsa_slave_create(), a second call to phy_attach() is made. This
results in the warning "PHY already attached". Remove this second,
redundant attaching of the phy.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>