Revert "Move all toString to be in users of HIDL libs."

This reverts commit 32bfbeb9ec923717eb4efaf03278ef2326b9325e.

Reason for revert: prebuilts have a problem with this.

Change-Id: I4ab5790b88ef137fdfbc4788121949c24bd0a307
diff --git a/EnumType.h b/EnumType.h
index 40cf199..ab9c4a7 100644
--- a/EnumType.h
+++ b/EnumType.h
@@ -79,7 +79,7 @@
 
     status_t emitTypeDeclarations(Formatter &out) const override;
     status_t emitGlobalTypeDeclarations(Formatter &out) const override;
-    status_t emitToStringDefinitions(Formatter &out) const;
+    status_t emitTypeDefinitions(Formatter &out, const std::string prefix) const override;
 
     status_t emitJavaTypeDeclarations(
             Formatter &out, bool atTopLevel) const override;