According to the datasheet, BCM5325 uses B53_PD_MODE_CTRL_25 register to
disable clocking to individual PHYs.
Only ports 1-4 can be enabled or disabled and the datasheet is explicit
about not toggling BIT(0) since it disables the PLL power and the switch.
Signed-off-by: Álvaro Fernández Rojas <noltari@xxxxxxxxx>