tree-optimization/105786 - avoid strlen replacement for pointers

This avoids matching strlen to a pointer result, avoiding ICEing
because of an integer adjustment using PLUS_EXPR on pointers.

2022-06-01  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105786
	* tree-loop-distribution.cc
	(loop_distribution::transform_reduction_loop): Only do strlen
	replacement for integer type reductions.

	* gcc.dg/torture/pr105786.c: New testcase.