Fix Incorrect Variable Check in SeparateSpecialRegionsInMemoryMap() (t…

…ianocore#143)

## Description

The variable used to check if we added entries to the memory map should
be MemoryMapEnd, not MapEntryEnd.

## Breaking change?
No

## How This Was Tested

Testing special regions

## Integration Instructions

N/A

MdeModulePkg/Core/Dxe/Misc/MemoryProtectionSupport.c

@@ -2046,7 +2046,7 @@ SeparateSpecialRegionsInMemoryMap (
   }
 
   // if we've created new records, sort the map
-  if ((UINTN)MapEntryInsert > (UINTN)MapEntryEnd) {
+  if ((UINTN)MapEntryInsert > (UINTN)MemoryMapEnd) {
     // Sort from low to high
     SortMemoryMap (
       MemoryMap,