Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

This includes the atomic_ -> qatomic_ rename that touches many files and is
prone to conflicts.

# gpg: Signature made Wed 23 Sep 2020 17:08:43 BST
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  qemu/atomic.h: rename atomic_ to qatomic_
  tests: add test-fdmon-epoll
  fdmon-poll: reset npfd when upgrading to fdmon-epoll
  gitmodules: add qemu.org vbootrom submodule
  gitmodules: switch to qemu.org meson mirror
  gitmodules: switch to qemu.org qboot mirror
  docs/system: clarify deprecation schedule
  virtio-crypto: don't modify elem->in/out_sg
  virtio-blk: undo destructive iov_discard_*() operations
  util/iov: add iov_discard_undo()
  virtio: add vhost-user-fs-ccw device
  libvhost-user: handle endianness as mandated by the spec
  MAINTAINERS: add Stefan Hajnoczi as block/nvme.c maintainer

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