dwc_otg: don't leak kernel address

Since commit ad67b74d ("printk: hash addresses printed with %p"),
an obfuscated kernel pointer is printed at boot:

    dwc_otg fe980000.usb: base=(____ptrval____)

Remove the the print completely, as it's useless without the address.

Signed-off-by: Matteo Croce <mcroce@redhat.com>