Default expand_vec_cond_expr_p code to ERROR_MARK

Default expand_vec_cond_expr_p code to ERROR_MARK

As we want to transition to only vcond_mask expanders the following
makes it possible to easier distinguish queries that rely on
vcond queries for expand_vec_cond_expr_p from those of vcond_mask
by for the latter having the comparison code defaulted to ERROR_MARK.

	* optabs-tree.h (expand_vec_cond_expr_p): Default the
	comparison code to ERROR_MARK.
	* match.pd: Remove unneded expand_vec_cond_expr_p args.
	* tree-vect-generic.cc (expand_vector_condition): Likewise.
	* tree-vect-loop.cc (vect_reduction_update_partial_vector_usage):
	Likewise.
	* tree-vect-stmts.cc (vectorizable_simd_clone_call): Likewise.
	(scan_store_can_perm_p): Likewise.
	(vectorizable_condition): Likewise.