tree-optimization/110669 - bogus matching of loop bitop

The matching code lacked a check that we end up with a PHI node
in the loop header.  This caused us to match a random PHI argument
now catched by the extra PHI_ARG_DEF_FROM_EDGE checking.

	PR tree-optimization/110669
	* tree-scalar-evolution.cc (analyze_and_compute_bitop_with_inv_effect):
	Check we matched a header PHI.

	* gcc.dg/torture/pr110669.c: New testcase.