Merge remote-tracking branch 'remotes/ehabkost/tags/x86-next-pull-request' into staging

Speculative store buffer bypass mitigation (CVE-2018-3639)

# gpg: Signature made Mon 21 May 2018 23:00:46 BST
# gpg:                using RSA key 2807936F984DC5A6
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>"
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost/tags/x86-next-pull-request:
  i386: define the AMD 'virt-ssbd' CPUID feature bit (CVE-2018-3639)
  i386: Define the Virt SSBD MSR and handling of it (CVE-2018-3639)
  i386: define the 'ssbd' CPUID feature bit (CVE-2018-3639)

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