cypress_m8: use usb_fill_int_urb where appropriate

Rather than directly filling in URB fields, it's safer to use
usb_fill_int_urb().  This improves robustness of the driver; URB
changes in the future will not go uninitialized here.  That point not
withstanding, this driver should at least be self-consistent.  Either
use usb_fill_int_urb() everywhere or don't bother with it all.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>