tblgen: Mechanically move dynamic_cast<> to dyn_cast<>.

Some of these dyn_cast<>'s would be better phrased as isa<> or cast<>.
That will happen in a future patch.

There are also two dyn_cast_or_null<>'s slipped in instead of
dyn_cast<>'s, since they were causing crashes with just dyn_cast<>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165646 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/CodeGenSchedule.cpp b/utils/TableGen/CodeGenSchedule.cpp
index bf4f2a3..fc101ee 100644
--- a/utils/TableGen/CodeGenSchedule.cpp
+++ b/utils/TableGen/CodeGenSchedule.cpp
@@ -59,7 +59,7 @@
     SmallVector<Regex*, 4> RegexList;
     for (DagInit::const_arg_iterator
            AI = Expr->arg_begin(), AE = Expr->arg_end(); AI != AE; ++AI) {
-      StringInit *SI = dynamic_cast<StringInit*>(*AI);
+      StringInit *SI = dyn_cast<StringInit>(*AI);
       if (!SI)
         throw "instregex requires pattern string: " + Expr->getAsString();
       std::string pat = SI->getValue();