The INVD instruction intercept performs emulation. Emulation can't be done
on an SEV guest because the guest memory is encrypted.

Provide a dedicated intercept routine for the INVD intercept. And since
the instruction is emulated as a NOP, just skip it instead.

Fixes: 1654efcb ("KVM: SVM: Add KVM_SEV_INIT command")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <a0b9a19ffa7fef86a3cc700c7ea01cb2731e04e5.1600972918.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>