For pre-launched VMs and SOS, vCPUs are created on BSP one by one; For post-launched VMs,
vCPUs are created under vmm_hypercall_lock protection. So vcpu_create is called sequentially.
Operation in vcpu_create don't need to be atomic.
Tracked-On: #1842
Signed-off-by: Li, Fei1 <fei1.li@intel.com>