Implement << operator for DexRegisterLocation::Kind.

This makes it comparable in DCHECK_EQ and similar methods.

Change-Id: I6b5b237be89325850ae6860d011fd6741189ab01
diff --git a/compiler/optimizing/stack_map_stream.cc b/compiler/optimizing/stack_map_stream.cc
index 4784de1..b44f508 100644
--- a/compiler/optimizing/stack_map_stream.cc
+++ b/compiler/optimizing/stack_map_stream.cc
@@ -63,8 +63,7 @@
 void StackMapStream::AddDexRegisterEntry(DexRegisterLocation::Kind kind, int32_t value) {
   if (kind != DexRegisterLocation::Kind::kNone) {
     // Ensure we only use non-compressed location kind at this stage.
-    DCHECK(DexRegisterLocation::IsShortLocationKind(kind))
-        << DexRegisterLocation::PrettyDescriptor(kind);
+    DCHECK(DexRegisterLocation::IsShortLocationKind(kind)) << kind;
     DexRegisterLocation location(kind, value);
 
     // Look for Dex register `location` in the location catalog (using the