usb: dwc3: gadget: remove unbalanced pm_runtime_put()

Previously the pm_runtime_get() call from __dwc3_gadget_ep_queue()
and corresponding pm_runtime_put() in dwc3_gadget_giveback() were
removed due to our modifications on how runtime PM is handled.
However commit 59d3a952e4f3 ("usb: dwc3: gadget: never call
->complete() from ->ep_queue()") was brought in via stable merge
and added back the pm_runtime_put() to the new function
dwc3_del_and_unmap_request() causing the PM usage_count to grow
more and more negative each time peripheral mode was started
and stopped. Remove this pm_runtime_put() as the negative count
causes host mode to not work due to xhci-plat child thinking that
its parent is not in RPM_ACTIVE state.

Change-Id: I5c055e26aa35d337cec7db441fe50b4ee05a7eb4
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>