usbdrv: support HID descriptors over 255 bytes

Implementing HID devices conforming to the Windows 8 Sensor API can produce quite large
HID descriptors - well over 255 bytes. This requires USB_CFG_LONG_TRANSFERS to be enabled
and also requires the recent patch to support large descriptors. That patch failed to enable
large HID descriptors but this is fixed by this commit.

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>