Merge remote-tracking branch 'remotes/kraxel/tags/fixes-20190402-pull-request' into...

fixes for 4.0 (audio, usb),

# gpg: Signature made Tue 02 Apr 2019 07:46:22 BST
# 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/fixes-20190402-pull-request:
  audio: fix audio timer rate conversion bug
  usb-mtp: remove usb_mtp_object_free_one
  usb-mtp: fix return status of delete
  hw/usb/bus.c: Handle "no speed matched" case in usb_mask_to_str()
  Revert "audio: fix pc speaker init"

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