UefiCpuPkg/PiSmmCpu: Don't allocate Token for SmmStartupThisAp

UefiCpuPkg/PiSmmCpu: Don't allocate Token for SmmStartupThisAp

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3199

When Token points to mSmmStartupThisApToken, this routine is called
from SmmStartupThisAp() in non-blocking mode due to
PcdCpuSmmBlockStartupThisAp == FALSE.

In this case, caller wants to startup AP procedure in non-blocking
mode and cannot get the completion status from the Token because there
is no way to return the Token to caller from SmmStartupThisAp().
Caller needs to use its specific way to query the completion status.

There is no need to allocate a token for such case so the 3 overheads
can be avoided:
1. Call AllocateTokenBuffer() when there is no free token.
2. Get a free token from the token buffer.
3. Call ReleaseToken() in APHandler().

Signed-off-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>