[NFC] [SILOpt] Explicitly specified flag defaults.

In preparation to change the default values, specify explicitly what
they are.

Author: nate-chandler

tools/sil-opt/SILOpt.cpp

@@ -139,11 +139,11 @@ static llvm::cl::opt<bool> EnableOSSAModules(
                    "form when optimizing."));
 
 static llvm::cl::opt<bool>
-    EnableCopyPropagation("enable-copy-propagation",
+    EnableCopyPropagation("enable-copy-propagation", llvm::cl::init(false),
                           llvm::cl::desc("Enable the copy propagation pass."));
 
 static llvm::cl::opt<bool> DisableCopyPropagation(
-    "disable-copy-propagation",
+    "disable-copy-propagation", llvm::cl::init(false),
     llvm::cl::desc("Disable the copy propagation pass."));
 
 namespace {