KVM: VMX: Expose SSBD properly to guests.

KVM: VMX: Expose SSBD properly to guests.

The X86_FEATURE_SSBD is an synthetic CPU feature - that is
it bit location has no relevance to the real CPUID 0x7.EBX[31]
bit position. For that we need the new CPU feature name.

Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")
CC: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: stable@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CVE-2018-3639 (x86)

(cherry-picked from https://patchwork.kernel.org/patch/10416823/)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>