libpayload: Fix OHCI some more

libpayload: Fix OHCI some more

OHCI works when USB_DEBUG is disabled, but not, when disabled.
This is because the controller requires some more time after a
schedule has finished.

Also improve compliance with the OHCI spec.

Change-Id: I4685cc485ff9c52b489fbaa352ab889671cff876
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/365
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>