[Ada] Fix for missing calls to Adjust primitive with nested generics

[Ada] Fix for missing calls to Adjust primitive with nested generics

2020-06-03  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* sem_ch12.adb (Denotes_Previous_Actual): Delete.
	(Check_Generic_Actuals): Do not special case array types whose
	component type denotes a previous actual.  Do not special case
	access types whose base type is private.
	(Check_Private_View): Remove code dealing with secondary types.
	Do not switch the views of an array because of its component.
	(Copy_Generic_Node): Add special handling for a comparison
	operator on array types.
	(Instantiate_Type): Do not special case access types whose
	designated type is private.
	(Set_Global_Type): Do not special case array types whose
	component type is private.