target/i386: define md-clear bit

target/i386: define md-clear bit

md-clear is a new CPUID bit which is set when microcode provides the
mechanism to invoke a flush of various exploitable CPU buffers by invoking
the VERW instruction.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20190515141011.5315-2-berrange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
(cherry picked from commit b2ae52101fca7f9547ac2f388085dbc58f8fe1c0)
Signed-off-by: Oguz Bektas <o.bektas@proxmox.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>