Merge remote-tracking branch 'remotes/kraxel/tags/usb-20190220-pull-request' into staging

usb: usb_ep_get() fixes

# gpg: Signature made Wed 20 Feb 2019 11:13:32 GMT
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>" [full]
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>" [full]
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>" [full]
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/usb-20190220-pull-request:
  usb: remove unnecessary NULL device check from usb_ep_get()
  usb: add device checks before redirector calls to usb_ep_get()
  usb: check device is not NULL before calling usb_ep_get()
  uhci: check device is not NULL before calling usb_ep_get()
  ohci: check device is not NULL before calling usb_ep_get()
  ehci: check device is not NULL before calling usb_ep_get()
  xhci: check device is not NULL before calling usb_ep_get()
  xhci: add asserts to help with static code analysis
  usb: rearrange usb_ep_get()

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