ARM: dts: BCM5301X: Remove cell properties from srab ports on Asus RT-AC88U

Remove #address-cells and #size-cells properties from the ports node of
&srab. They are already defined on bcm5301x.dtsi, there's no need to define
them again.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Acked-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>