usb: dwc3: add rx_detect to polling lfps quirk

This patch adds RX_DETECT to Polling.LFPS control quirk, and some special
platforms can configure that if it is needed.

[ balbi@ti.com : added DeviceTree binding documentation ]

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>