Cleanup way elidable types are determined.

After adding the pointer type, it didn't make sense for elidable types
to be specified in canElideCallback. Now the decision as to whether a
specific type is elidable has been moved into 'isElidableType' on the
Type class.

Bug: 33298401
Test: mma in hardware/interfaces
Change-Id: I66cbaed4c533013a52e59fc8e7edcdabc9ab9f20
diff --git a/ScalarType.h b/ScalarType.h
index 0ff8ec5..80bc9a0 100644
--- a/ScalarType.h
+++ b/ScalarType.h
@@ -41,6 +41,7 @@
 
     bool isScalar() const override;
 
+    bool isElidableType() const override;
     const ScalarType *resolveToScalarType() const override;
 
     std::string typeName() const override;