ada: Fix internal error on bit-packed array type with Volatile_Full_Access

ada: Fix internal error on bit-packed array type with Volatile_Full_Access

The problem occurs when the component type is a record type with default
values for the initialization procedure of the (base) array type, because
the compiler is trying to generate a full access for a parameter of the
base array type, which does not make sense.

gcc/ada/ChangeLog:

	PR ada/116551
	* gcc-interface/trans.cc (node_is_atomic) <N_Identifier>: Return
	false if the type of the entity is an unconstrained array type.
	(node_is_volatile_full_access) <N_Identifier>: Likewise.