usb: dwc2: Allow entering hibernation from USB_SUSPEND interrupt

Do changes to allow entering hibernated state from USB_SUSPEND
interrupt. All code is added under if conditions and mustn't impact
existing functionality.

Signed-off-by: Vardan Mikayelyan <mvardan@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Grigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>