BACKPORT: usb: dwc3: gadget: move cmd_endtransfer to extra function

This patch adds the extra function __dwc3_stop_active_transfer to
consolidate the same codepath.

Bug: 276227797
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20220306211251.2281335-3-m.grzeschik@pengutronix.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit e192cc7b)
Change-Id: I200a354ae39afb6d58a92f98fef183a51e3810bb