usb: dwc2: fix role switch breakage

Commit beb7e592

 "staging: dwc2: add check on dwc2_core_reset
return" broke the B -> A role switching on OTG-enabled platforms.
This commit fixes it.

Reported-by: Dinh Nguyen <dinguyen@altera.com>
Tested-by: Dinh Nguyen <dinguyen@altera.com>
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>