SecurityPkg: Remove Support for _DSM Memory Clear

[os-d]

Description

_DSM Memory Clear is not used, so this code removes it.

Cherry-picked from f911628.

• Impacts functionality?
  • Functionality - Does the change ultimately impact how firmware functions?
  • Examples: Add a new library, publish a new PPI, update an algorithm, ...
• Impacts security?
  • Security - Does the change have a direct security impact on an application,
    flow, or firmware?
  • Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
• Breaking change?
  • Breaking change - Will anyone consuming this change experience a break
    in build or boot behavior?
  • Examples: Add a new library class, move a module to a different repo, call
    a function in a new library class in a pre-existing module, ...
• Includes tests?
  • Tests - Does the change include any explicit test code?
  • Examples: Unit tests, integration tests, robot tests, ...
• Includes documentation?
  • Documentation - Does the change contain explicit documentation additions
    outside direct code modifications (and comments)?
  • Examples: Update readme file, add feature readme file, link to documentation
    on an a separate Web page, ...

How This Was Tested

From 2311.

Integration Instructions

N/A.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@                Coverage Diff                @@
##             release/202405     #296   +/-   ##
=================================================
  Coverage                  ?   91.05%           
=================================================
  Files                     ?       11           
  Lines                     ?     1778           
  Branches                  ?      200           
=================================================
  Hits                      ?     1619           
  Misses                    ?      143           
  Partials                  ?       16           

Flag	Coverage Δ
SecurityPkg	91.05% <ø> (?)

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[kuqin12]

Should we have this split into two changes? The tcg2smm one seems to be removing a

[kuqin12]

This change functionally seems fine, but touches 2 modules at the same time. I guess it will not be checked into edk2 as is.

[os-d]

I will split this into two commits.