UefiCpuPkg: Fix potential spinLock issue in SmmStartupThisAp

UefiCpuPkg: Fix potential spinLock issue in SmmStartupThisAp

Due to needs a tackling the deficiency of the AP API, it's necessary to
ensure that in non-blocking mode previous AP executed command is
finished before starting new one.

To remedy above:
  1) execute AcquireSpinLock instead AcquireSpinLockOrFail - this will
     ensure time "window" to eliminate potential race condition between
     BSP and AP spinLock release in non-blocking mode.
     This also will eliminate possibility to start executing new AP
     function before last is finished.
  2) remove returns EFI_STATUS - EFI_NOT_READY - in new scenario returned
     status is not necessary to caller.

Signed-off-by: Damian Nikodem <damian.nikodem@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Benjamin You <benjamin.you@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Krzysztof Rusocki <krzysztof.rusocki@intel.com>