Merge remote-tracking branch 'remotes/kraxel/tags/pull-usb-20160419-1' into staging

ehci: fix (s)iTD looping issue (CVE-2015-8558) in a different way.

# gpg: Signature made Tue 19 Apr 2016 07:22:22 BST using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"

* remotes/kraxel/tags/pull-usb-20160419-1:
  Revert "ehci: make idt processing more robust"
  ehci: apply limit to iTD/sidt descriptors

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>