If usb controller is in partial power down, any write to registers may
cause unpredictable behavior.
Thus, prevent any new request submission once controller is in partial
power down.
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>