commit 9bafa56c upstream.

Zero is a valid value for a microframe number. So remove the bogus
test for non-zero in dwc3_gadget_start_isoc().
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>