Merge remote-tracking branch 'remotes/aperard/tags/pull-xen-20200407' into staging

Xen queue for QEMU 5.0

- Fix for xen-block.
- A fix for a Coverity false positive in xen-usb.
- Update MAINTAINERS to add xen-usb.c to Xen section.

# gpg: Signature made Tue 07 Apr 2020 16:21:16 BST
# gpg:                using RSA key F80C006308E22CFD8A92E7980CF5572FD7FB55AF
# gpg:                issuer "anthony.perard@citrix.com"
# gpg: Good signature from "Anthony PERARD <anthony.perard@gmail.com>" [marginal]
# gpg:                 aka "Anthony PERARD <anthony.perard@citrix.com>" [marginal]
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: 5379 2F71 024C 600F 778A  7161 D8D5 7199 DF83 42C8
#      Subkey fingerprint: F80C 0063 08E2 2CFD 8A92  E798 0CF5 572F D7FB 55AF

* remotes/aperard/tags/pull-xen-20200407:
  MAINTAINERS: Add xen-usb.c to Xen section
  xen-block: Fix uninitialized variable
  hw/usb/xen-usb.c: Pass struct usbback_req* to usbback_packet_complete()

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