usb: chipidea: Fix ULPI on imx51

Workaround introduced for i.MX53 in be9cae24 ("usb: chipidea:
imx: Fix ULPI on imx53") seems to be applicable in case of i.MX51 as
well. Running latest kernel on ZII RDU1 Board (imx51-zii-rdu1.dts)
exhibits a kernel frozen on PORTSC access and applying the workaround
resolves the issue.

Fixes: be9cae24

 ("usb: chipidea: imx: Fix ULPI on imx53")
Cc: Peter Chen <peter.chen@nxp.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Chris Healy <cphealy@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Tested-By: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>