tree-optimization/102853 - avoid trapping types in split_constant_offset

This avoids running into the assert in compute_distributive_range when
starting the analysis with operations in a trapping type.

2021-10-20  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102853
	* tree-data-ref.c (split_constant_offset_1): Bail out
	immediately if the expression traps on overflow.