usb: dwc3: Add support for device L1 exit

For the usb31 IP and from version 2.90a of the usb3 IP, the core
supports HW exit from L1 in HS. Enable it, otherwise the controller may
never exit from LPM to do a transfer.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>