net: phy: dp83867: IO impedance is not dependent on RGMII delay

The driver would only set the IO impedance value when RGMII internal
delays were enabled.  There is no reason for this.  Move the IO
impedance block out of the RGMII delay block.

Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Trent Piepho <tpiepho@impinj.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>