Freed allocated request for ep0 to prevent memory leak in case when
dwc2_driver_probe() failed.

Cc: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: NStefan Wahren <stefan.wahren@i2se.com>
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Acked-by: NMinas Harutyunyan <hminas@synopsys.com>
Signed-off-by: NGrigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>