[BOOT] Add stubs to complete MmPaInitialize()

MmPaInitialize() is now complete
Added BlpMmInitializeConstraints() and MmMdRemoveRegionFromMdlEx()

BOOT/ENVIRON/LIB/MM/mmmd.c

@@ -347,9 +347,9 @@ Routine Description:
 
 Arguments:
 
-    Mdl - the MDL to remove Descriptor from.
+    Mdl - MDL to remove Descriptor from.
 
-    Descriptor - the descriptor to remove from Mdl.
+    Descriptor - Descriptor to remove from Mdl.
 
 Return Value:
 
@@ -386,6 +386,67 @@ Return Value:
     }
 }
 
+NTSTATUS
+MmMdRemoveRegionFromMdlEx (
+    IN PMEMORY_DESCRIPTOR_LIST Mdl,
+    IN ULONGLONG FirstPage,
+    IN ULONGLONG PageCount,
+    IN ULONG Flags,
+    OUT PMEMORY_DESCRIPTOR_LIST Unused
+    )
+
+/*++
+
+Routine Description:
+
+    Removes a region from a MDL.
+
+Arguments:
+
+    Mdl - MDL to remove the region from.
+
+    FirstPage - The first page in the region.
+
+    PageCount - The number of pages in the region.
+
+    Flags - MDL_OPERATION_FLAGS_*.
+
+    Unused - Unused.
+
+Return Value:
+
+    None.
+
+--*/
+
+{
+    ULONGLONG RemoveEnd, DescriptorEnd;
+    PLIST_ENTRY Entry;
+    PMEMORY_DESCRIPTOR Descriptor;
+    MEMORY_DESCRIPTOR RemovedDescriptor;
+
+    (VOID)Flags;
+    (VOID)Unused;
+
+    RemoveEnd = FirstPage + PageCount;
+    Entry = Mdl->Head->Flink;
+    while (Entry != Mdl->Head) {
+        Descriptor = (PMEMORY_DESCRIPTOR)Entry;
+        DescriptorEnd = Descriptor->FirstPage + Descriptor->PageCount;
+
+        RtlCopyMemory(&RemovedDescriptor, Descriptor, sizeof(MEMORY_DESCRIPTOR));
+
+        // if (FirstPage <= Descriptor->FirstPage && Descriptor->FirstPage < RemoveEnd) {
+        // }
+    }
+
+    //
+    // TODO: Finish this function.
+    //
+
+    return STATUS_SUCCESS;
+}
+
 NTSTATUS
 MmMdFreeDescriptor (
     IN PMEMORY_DESCRIPTOR Descriptor