usb: devio: update max count of DPs per interval for ISOC

The failure happened when I tried to send up to 96DPs per an interval
for SSP ISOC transations by libusb, this is used to verify SSP ISOC
function of USB3 GEN2 controller, so update it as 96DPs.
(refer usb3.1r1.0 section 8.12.6 Isochronous Transactions)

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>