QuarkPlatformPkg/PlatformInit: Clear memory based on TCG MOR request

If TCG Memory Overwrite Request is set, then clear all memory
available for use by an OS.  An OS may optionally use embedded
SRAM in Quark SoC X1000, so the embedded SRAM should is cleared
too.  TCG MOR requests are communicated through a UEFI variable.
This module reads UEFI variable to check state of MOR request.

Cc: Kelly Steele <kelly.steele@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Kelly Steele <kelly.steele@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19776 6f19259b-4bc3-4df7-8a09-765794883524