This patch makes some simple changes to the way the UHCI driver does short
packet detection.  The current implementation is incorrect in several
ways:

	The Short-Packet-Detect flag is set for OUT transfers, which
	yields undefined behavior according to the UHCI spec.

	It's not set for URBs with URB_SHORT_NOT_OK, which is just the
	opposite of what we want!  Those are the ones where short packets
	do matter.

	It is set for the last packet in a transfer, which causes an
	unnecessary pause in the data flow (except of course that the
	pause _is_ necessary when URB_SHORT_NOT_OK is set).

The patch also implements the URB_NO_INTERRUPT flag for bulk transfers,
which can help improve system performance by reducing interrupt overhead.