MicrocodeMeasurementDxe debug string correction (#303)

## Description

In a platform with memory protections, the incorrect debug string
argument (%a paired with an EFI_STATUS input) resulted in a CPU
exception (based on what was in the uninitialized memory for the
string).

For each item, place an "x" in between `[` and `]` if true. Example:
`[x]`.
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- [ ] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [x] 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
After correcting debug string, platform no longer experienced an
exception D (General Protection)

## Integration Instructions
N/A

---------

Signed-off-by: Aaron <105021049+apop5@users.noreply.github.com>
Co-authored-by: Michael Kubacki <michael.kubacki@microsoft.com>

UefiCpuPkg/MicrocodeMeasurementDxe/MicrocodeMeasurementDxe.c

@@ -238,7 +238,7 @@ MeasureMicrocodePatches (
        TotalMicrocodeSize)
       );
   } else {
-    DEBUG ((DEBUG_ERROR, "ERROR: TpmMeasureAndLogData failed with status %a!\n", Status));
+    DEBUG ((DEBUG_ERROR, "ERROR: TpmMeasureAndLogData failed with status %r!\n", Status));  // MU_CHANGE
   }
 
   FreePool (Offsets);