QuarkPlatformPkg/PlatformSecLib: Fix stack pointer issue in Flat32.S

QuarkPlatformPkg/PlatformSecLib: Fix stack pointer issue in Flat32.S

ESP should be set to top of eSRAM range that aligns with Flat32.asm. Because CPU
BIST data will be located at top of STACK, this issue leads Platform Sec Lib
cannot get the correct CPU BIST information.

This fix is to address below issue:
  https://tianocore.acgmultimedia.com/show_bug.cgi?id=123

Cc: Steven Shi <Steven.shi@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Kelly Steele <kelly.steele@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>