usb: dwc2_udc_otg: use the phy bulk API to get phys

Use the phy bulk API to get a group of phys

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: Weijie Gao <weijie.gao@mediatek.com>