UPSTREAM: usb: dwc3: gadget: Simplify skipping of link TRBs

UPSTREAM: usb: dwc3: gadget: Simplify skipping of link TRBs

Make the skipping of the link TRBS built-in to the increment operation.
This simplifies the code wherever we increment the trb index and ensures
that we never end up pointing to a link trb.

Change-Id: I72063fcf672a07c3ac5132c488e75df1a6d91e94
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Wu Liang feng <wulf@rock-chips.com>
(cherry picked from commit dca0119c3ab69fea2429ec2db7e3686614bd1439)