usb: ohci-nxp: fix use of integer as pointer

usb: ohci-nxp: fix use of integer as pointer

The hcd pointer in ohci_hcd_nxp_probe() is
being initialised with a 0, so fix to NULL to
avoid the following sparse warning:

drivers/usb/host/ohci-nxp.c:153:31: warning: Using plain integer as NULL pointer

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Acked-by: Sylvain Lemieux <slemieux.tyco@gmail.com>
Link: https://lore.kernel.org/r/20191015141945.16067-1-ben.dooks@codethink.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>