KVM: VMX: Fold loaded_vmcs_init() into alloc_loaded_vmcs()

Subsume loaded_vmcs_init() into alloc_loaded_vmcs(), its only remaining
caller, and drop the VMCLEAR on the shadow VMCS, which is guaranteed to
be NULL.  loaded_vmcs_init() was previously used by loaded_vmcs_clear(),
but loaded_vmcs_clear() also subsumed loaded_vmcs_init() to properly
handle smp_wmb() with respect to VMCLEAR.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200321193751.24985-3-sean.j.christopherson@intel.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>