vect: Use loop len in vectorizable_scan_store.

vect: Use loop len in vectorizable_scan_store.

On riscv we ICE because we use SELECT_VL for a vectorizable_scan_store
that calls vect_get_data_ptr_increment without a loop_lens argument.

This patch just gets the loop_lens and passes them along.

gcc/ChangeLog:

	* tree-vect-stmts.cc (vectorizable_scan_store): Pass loop_lens
	to vect_get_data_ptr_increment.