mediatek: routerich be7200: fix usb issue

mediatek: routerich be7200: fix usb issue

This commit fixes non-working USB port:
---
[    5.294036] xhci-mtk 11200000.usb: error -EPERM: Failed to get supply 'vbus'
[    5.301163] xhci-mtk 11200000.usb: error -EPERM: Failed to get regulators
[    5.307938] xhci-mtk 11200000.usb: probe with driver xhci-mtk failed with error -1
---

While testing the USB power on/off functionality during the previous
commit, I didn't sufficiently test the actual operation of the USB
devices.

Fixes: ff5e66a9208a ("mediatek: add support for Routerich BE7200")
Signed-off-by: Mikhail Zhilkin <csharper2005@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21795
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>