ramips: Get rt3050 ethernet ports to be disabled from the device tree.
This patch allows configuring ports to be disabled in the device tree; this
saves power, since disabling ports here actually disables power to ethernet
Line 444 enables all ethernet ports, so line 487 is getting zero ports to be
disabled, except for port 5 in SoCs where this is not implemented as it will
be sticky disabled in register POC0. Because of this, the code will still read
the switch configuration and OR it to the device tree setting.