ARM: dts: armada-38x: fix NETA lockup when repeatedly switching speeds

To support the change in "phy: armada-38x: fix NETA lockup when
repeatedly switching speeds" we need to update the DT with the
additional register.

Fixes: 14dc100b ("phy: armada38x: add common phy support")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>