too, but that's not critical): real hubs send port status change
notifications until acknowledged, ehci/ohci send only once so there is
a chance that this gets lost if notifications are disabled during a scan.
The temporary fix is to force a rescan; the real fix will involve a
change in interrupt handling in ehci/ohci which needs more work and
testing.
ehci is critical because a port status change during scan regularely
happens if a full/lowspeed device is connected, due to the handover
process.
Fixes a problem where full/lowspeed devices were not reattached after
a disconnect, reported by Kouichirou Hiratsuka and Juan RP
on current-users.
27622eb242