Merge remote-tracking branch 'kraxel/usb.79' into staging

# By Gerd Hoffmann (7) and Hans de Goede (3)
# Via Gerd Hoffmann
* kraxel/usb.79:
  usb-tablet: Don't claim wakeup capability for USB-2 version
  usb: update docs for bus name change
  usb-hub: report status changes only once
  usb-hub: limit chain length
  xhci: zap unused name field
  xhci: remove unimplemented printfs
  xhci: remove leftover debug printf
  xhci: fix numintrs sanity checks
  usb-redir: Add flow control support
  usb-redir: Fix crash on migration with no client connected