USB: EHCI: fix counting of transaction error retries

commit ef4638f955f2c4a667c8af20769d03f5ed3781ca upstream.

This patch (as1274) simplifies the counting of transaction-error
retries.  Now we will count up from 0 to QH_XACTERR_MAX instead of
down from QH_XACTERR_MAX to 0.

The patch also fixes a small bug: qh->xacterr was not getting
initialized for interrupt endpoints.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Matthijs Kooijman <matthijs@stdin.nl>
Cc: Reinoud Koornstra <koornstra@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>