usb: dwc3: Dont release wakeup source during usb restart

When changing USB speed via sysfs, the device might utilize the
idle time between DISCONNECT and CONNECT events and enter suspend.
As a result the pending CONNECT might get delayed thus pushing USB
enumeration during the next resume. Avoid this by not releasing the
wakeup source when usb restart is in progress.

Change-Id: I754b76eb7b36923a2dcd4d58587101750d1cd83c
Signed-off-by: Elson Roy Serrao <eserrao@codeaurora.org>