ada: Flatten Is_Build_In_Place_Aggregate_Return predicate

ada: Flatten Is_Build_In_Place_Aggregate_Return predicate

The predicate is passed an aggregate node and goes up its parent chain,
but that's unnecessary because Convert_To_Assignments has already done
so in the case of a record aggregate and Expand_Array_Aggregate does not
fully support intermediate conditional expressions yet.

gcc/ada/ChangeLog:

	* exp_aggr.adb (Is_Build_In_Place_Aggregate_Return): Directly test
	the node and remove dead code for extended return statements.