Remove unused vcond{,u,eq} expander infrastructure

Now that we no longer exercise vcond{,u,eq} patterns remove unused
infrastructure.

	* optabs-query.h (get_vcond_icode): Remove.
	(get_vcond_eq_icode): Likewise.
	* optabs-tree.h (expand_vec_cond_expr_p): Remove code
	argument.
	* optabs-tree.cc (expand_vec_cond_expr_p): Likewise.
	(vcond_icode_p): Remove.
	(vcond_eq_icode_p): Likewise.
	* optabs.h (can_vcond_compare_p): Remove.
	* optabs.cc (can_vcond_compare_p): Likewise.