usb: dwc2: gadget: kill ep0 requests before reinitializing core

Make sure there are no requests pending on ep0 before reinitializing
core. Otherwise, dwc2_hsotg_enqueue_setup will fail afterwards.

Also, take hsotg->lock before calling
dwc2_hsotg_core_init_disconnected() from dwc2_conn_id_status_change()
as dwc2_hsotg_complete_request() expect lock to be held.

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>