usb: chipidea: ci13xxx_imx: check if 'data->phy_np' is not NULL

Similarly as it is done in ci13xxx_imx_remove(), only calls of_node_put if
data->phy_np is not NULL.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>