UefiCpuPkg/MpInitLib: Optimize get processor number performance.

Current function has low performance because it calls GetApicId
in the loop, so it maybe called more than once.

New logic call GetApicId once and base on this value to search
the processor.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jeff Fan <vanjeff_919@hotmail.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>