This fixes the heuristic deriving an actual object type from a
MEM_REFs pointer operand to use the more sensible type of an
actual object instead of the pointed to type.

2020-03-20  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/94266
	* gimple-ssa-sprintf.c (get_origin_and_offset): Use the
	type of the underlying object to adjust for the containing
	field if available.