[BOOT] Improve TODO comments

BOOT/ENVIRON/LIB/MM/mm.c

@@ -41,7 +41,7 @@ Return Value:
 
 {
     //
-    // TODO: Implement this.
+    // TODO: Implement this routine.
     //
 
     return STATUS_SUCCESS;

BOOT/ENVIRON/LIB/MM/mmmd.c

@@ -83,7 +83,7 @@ Return Value:
     }
 
     //
-    // TODO: Incomplete.
+    // TODO: Implement the rest of this routine.
     //
     ConsolePrint(L"MmMdpHasPrecedence() is incomplete\r\n");
     return TRUE;
@@ -441,7 +441,7 @@ Return Value:
     }
 
     //
-    // TODO: Finish this function.
+    // TODO: Implement the rest of this routine.
     //
 
     return STATUS_SUCCESS;
@@ -490,7 +490,7 @@ Return Value:
 
     //
     // Free the descriptor from the heap.
-    // TODO: Use BlMmFreeHeap()
+    // TODO: Use BlMmFreeHeap().
     //
     ConsolePrint(L"MmMdFreeDescriptor(): need BlMmFreeHeap() to free descriptor\r\n");
     return STATUS_NOT_IMPLEMENTED;
@@ -565,6 +565,7 @@ Return Value:
     PMEMORY_DESCRIPTOR Descriptor;
 
     if (MmGlobalMemoryDescriptorsUsed >= MmGlobalMemoryDescriptorCount) {
+        DebugPrint(L"MmMdInitDescriptor(): No free descriptors available\r\n");
         return NULL;
     }