usb: dwc2: host: clear pending interrupts prior hibernation

If an interrupt rises during hibernation process, dwc2 will assert
interrupt line to interrupt controller. If interrupt is level
sensitive, interrupt handler will be called in a loop because dwc2
will not be able to clear it while controller is hibernated.
Thus, clear all controller interrupts before hibernation entry.

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>