usb: dwc3: gadget: Cleanup SG handling

The current logic in dwc3 driver is tracking req->num_queued_sgs and
req->sg. But they can be checked base on the num_pending_sgs and
num_trbs. They are redundant and can complicate the SG logic. Let's
remove them.

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/96c7bf8f6b3e91e607d5b78ea51cb1d00c614eaf.1731545781.git.Thinh.Nguyen@synopsys.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>