UPSTREAM: usb: dwc3: gadget: simplify run_stop() break condition

UPSTREAM: usb: dwc3: gadget: simplify run_stop() break condition

it's clear now that when is_on=true, we must loop
until DWC3_DSTS_DEVCTRLHLT clears; while when
is_on=false we must loop until DWC3_DSTS_DEVCTRLHLT
gets set.

Instead of adding actual if() statements, we can
rely on XOR operation to evaluate to true only when
the above conditions apply. Then, we can move the
break condition back to the while() statement
together with our timeout check and the resulting
code is very compact and simpler to read.

Change-Id: Id540c7422cd1d7e00120c26353d99e2e9888ea26
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Wu Liang feng <wulf@rock-chips.com>
(cherry picked from commit b6d4e16e831376b676edb3463f2bdaa192e5f7be)