usb: dwc3: gadget: Fix looping of queued SG entries

usb: dwc3: gadget: Fix looping of queued SG entries

The dwc3_request->num_queued_sgs is decremented on completion. If a
partially completed request is handled, then the
dwc3_request->num_queued_sgs no longer reflects the total number of
num_queued_sgs (it would be cleared).

Correctly check the number of request SG entries remained to be prepare
and queued. Failure to do this may cause null pointer dereference when
accessing non-existent SG entry.

Cc: stable@vger.kernel.org
Fixes: c96e6725db9d ("usb: dwc3: gadget: Correct the logic for queuing sgs")
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/d07a7c4aa0fcf746cdca0515150dbe5c52000af7.1731545781.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>