usb: gadget/imx-udc: remove usage of deprecated symbol USBD_INT0

Since v2.6.34-rc2~66^2~5^2~47 USBD_INT0 is deprecated in favour of
MX1_USBD_INT0.  So use the new name.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>