usb: dwc2: gadget: exit hibernation before power down

When disconnecting cable, controller will detect a suspend condition
and enter partial power down. If vbus_session is called by the phy
driver during hibernation, make sure controller exit hibernation
before it is accessed.

Signed-off-by: Jianqiang Tang <jianqiang.tang@intel.com>
Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
Tested-by: Robert Baldyga <r.baldyga@samsung.com>
Tested-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Tested-by: John Youn <johnyoun@synopsys.com>
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>