usb: chipidea: imx: check data->usbmisc_data against NULL before access

usb: chipidea: imx: check data->usbmisc_data against NULL before access

As usbmisc_data is optional, so add the check before access its member,
this fix below static checker warning:
drivers/usb/chipidea/ci_hdrc_imx.c:438 ci_hdrc_imx_probe()
warn: 'data->usbmisc_data' can also be NULL
which is introduced by Patch 15b80f7c3a7f:
"usb: chipidea: imx: enable vbus and id wakeup only for OTG events"

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Li Jun <jun.li@nxp.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>