Watchdog: pcwd_usb: remove CONFIG_USB_DEBUG usage

CONFIG_USB_DEBUG is going away, and all of the other USB drivers no
longer rely on "debug" module parameters for debugging lines, so move
the pcwd_usb driver to use the dynamic debug infrastructure to be more
in line with the rest of the kernel.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Wim Van Sebroeck <wim@iguana.be>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>