In the EHCI driver, itd->usecs[8] is used in periodic_usecs(), indexed by
uframe.  For an ITD's unused uframes it is 0, else it contains the same
value as itd->stream->usecs.  To check if an ITD's uframe is used, we can
instead test itd->hw_transaction[uframe]:  if used, it will be nonzero no
matter what endianess is used.

This patch replaces those two uses, eliminates itd->usecs[], and saves
eight bytes from each ITD.
Signed-off-by: NKarsten Wiese <fzu@wemgehoertderstaat.de>
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>