Intel/WhiskeylakeOpenBoardPkg: Simplify microcode related PCD usage

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3334



There are following PCDs in IntelFsp2WrapperPkg for microcode location:

* IntelFsp2WrapperPkg:
  PcdCpuMicrocodePatchAddress
  PcdCpuMicrocodePatchRegionSize
  PcdFlashMicrocodeOffset

The change simplify the platform code to use following PCDs instead:
* MinPlatformPkg
  PcdFlashFvMicrocodeOffset
  PcdFlashFvMicrocodeBase = $(BIOS_BASE) + PcdFlashFvMicrocodeOffset
  PcdFlashFvMicrocodeSize
  PcdMicrocodeOffsetInFv <NEW>

Signed-off-by: Jason Lou <yun.lou@intel.com>
Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>