usb2: Devices can't resume host from suspend

It's been known for ages, but I don't think there's an issue for it, so here it goes.

When usb-otg2 (38200000.usb) is allowed to suspend, it doesn't get woken up by any activity from the devices.

The most noticeable symptom is that any incoming calls or messages don't get noticed until something makes the host controller wake up (querying the modem or accessing SD card). Also, turning the modem on while USB host is suspended makes the system not notice it until host gets resumed.

(this doesn't happen when turning the modem off - in that case, the host gets woken up correctly; however, it seems that's only because of rfkill_hks which causes ModemManager to wake the bus up)

Note: usb-otg2 suspend is not enabled by default.

Test with:

echo auto | sudo tee /sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/power/control
echo auto | sudo tee /sys/devices/platform/soc@0/38200000.usb/power/control