apm821xx: fix WD MyBook Live DUO USB-Port

apm821xx: fix WD MyBook Live DUO USB-Port

where to begin? the USB regulator settings were just
a part of the issue. With them changed, according to
the forum it still failed when a USB device was
connected to the port with:

dwc2 4bff80000.usbotg: dwc2_restore_global_registers: no global registers to restore
dwc2 4bff80000.usbotg: dwc2_exit_partial_power_down: failed to restore registers
dwc2 4bff80000.usbotg: exit partial_power_down failed
dwc2 4bff80000.usbotg: HC died; cleaning up

One clue was found upstream in
commit cc10ce0c51b1 ("usb: dwc2: disable power_down on Amlogic devices")

|Disable power_down by setting the parameter to
|DWC2_POWER_DOWN_PARAM_NONE. This fixes a problem on various Amlogic
|Meson SoCs where USB devices are only recognized when plugged in before
|booting Linux. A hot-plugged USB device was not detected even though the
|device got power (my USB thumb drive for example has an LED which lit
|up).
|[...]

the same method proposed there worked with APM821xx's USB IP-Core.

Link: https://forum.openwrt.org/t/wd-my-book-duo-usb/111926/2
Reported-by: thwe and takimata (openwrt forum)
Fixes: b70d3557e05 ("apm821xx: clean up gpio-hogs")
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>