i386: Add spec-ctrl CPUID bit
    
    Add the feature name and a CPUID_7_0_EDX_SPEC_CTRL macro.
    
    Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
    Message-Id: <20180109154519.25634-4-ehabkost@redhat.com>
    Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
    (cherry picked from commit a2381f0934432ef2cd47a335348ba8839632164c)
    Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>