usb: wusbcore: change WA_SEGS_MAX to a legal value

change WA_SEGS_MAX to a number that is legal according to the WUSB
spec.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>