usb: chipidea: imx: Add usb_phy_shutdown at probe's error path

If not, the PHY will be active even the controller is not in use.
We find this issue due to the PHY's clock refcount is not correct
due to -EPROBE_DEFER return after phy's init.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>