[Ada] Separate building of equality from other dispatching routines

[Ada] Separate building of equality from other dispatching routines

gcc/ada/

	* exp_ch3.adb (Make_Predefined_Primitive_Specs): Move code for
	spec of dispatching equality.
	(Predefined_Primitive_Bodies): Move code for body if dispatching
	equality.
	(Make_Predefined_Primitive_Eq_Spec): Separated code for spec of
	dispatching equality.
	(Predefined_Primitive_Eq_Body): Separated code for body of
	dispatching equality.
	* exp_ch3.ads: Update.