KVM: SVM: Remove the need to trigger an UNBLOCK event on AP creation

All SNP APs are initially started using the APIC INIT/SIPI sequence in
the guest. This sequence moves the AP MP state from
KVM_MP_STATE_UNINITIALIZED to KVM_MP_STATE_RUNNABLE, so there is no need
to attempt the UNBLOCK.

As it is, the UNBLOCK support in SVM is only enabled when AVIC is
enabled. When AVIC is disabled, AP creation is still successful.

Remove the KVM_REQ_UNBLOCK request from the AP creation code and revert
the changes to the vcpu_unblocking() kvm_x86_ops path.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>