KVM: VMX: Allocate VPID after initializing VCPU

Do VPID allocation after calling the common kvm_vcpu_init() as a step
towards doing vCPU allocation (via kmem_cache_zalloc()) and calling
kvm_vcpu_init() back-to-back.  Squishing allocation and initialization
together will eventually allow the sequence to be moved to arch-agnostic
creation code.

Note, the VPID is not consumed until KVM_RUN, slightly delaying its
allocation should have no real function impact.  VPID allocation was
arbitrarily placed in the original patch, commit 2384d2b3

 ("KVM:
VMX: Enable Virtual Processor Identification (VPID)").

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>