ARM: dts: orion5x: Configure WNR854T ethernet PHY LEDs

The default PHY configuration disables most of the LEDs. The following
configures the ethernet activity LEDs as Netgear intended.

[gregory.clement@free-electrons.com: fix commit title]
Signed-off-by: Jamie Lentin <jm@lentin.co.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>