[TableGen] Replace some calls to ListInit::getSize() with ListInit::empty() if it was just comparing to 0. NFC.

llvm-svn: 237340
diff --git a/llvm/utils/TableGen/CodeGenMapTable.cpp b/llvm/utils/TableGen/CodeGenMapTable.cpp
index 8abea48..b52a91d 100644
--- a/llvm/utils/TableGen/CodeGenMapTable.cpp
+++ b/llvm/utils/TableGen/CodeGenMapTable.cpp
@@ -128,7 +128,7 @@
     ListInit *ColValList = MapRec->getValueAsListInit("ValueCols");
 
     // Each instruction map must specify at least one column for it to be valid.
-    if (ColValList->getSize() == 0)
+    if (ColValList->empty())
       PrintFatalError(MapRec->getLoc(), "InstrMapping record `" +
         MapRec->getName() + "' has empty " + "`ValueCols' field!");