Redefine fqname in hidl-gen_y.yy

There is an inconsistency in hidl-gen_y.yy that fqname does not
mean an FQName object, but a Type object. Redefined fqname to create
an FQName object only, and rename the original fqname rule to fqtype.

This also propagates to AST::lookupType and Scope::lookupType to
take an FQName object instead of a plain string.

Test: `mma`
Test: `make hidl_test && adb sync && adb shell hidl_test`
Change-Id: I5d35192fa5fa9752b10bd9e7d339eadc5cdb78c0
diff --git a/AST.h b/AST.h
index 2950a6f..1f9d4f0 100644
--- a/AST.h
+++ b/AST.h
@@ -66,7 +66,7 @@
     // Look up a type by FQName, "pure" names, i.e. those without package
     // or version are first looked up in the current scope chain.
     // After that lookup proceeds to imports.
-    Type *lookupType(const char *name);
+    Type *lookupType(const FQName &fqName);
 
     void addImportedAST(AST *ast);