tree-optimization/118569 - LC SSA broken after unrolling

tree-optimization/118569 - LC SSA broken after unrolling

The following amends the previous fix to mark all of the loop BBs
as need to be scanned for new LC PHI uses when its nesting parents
changed, noticing one caller of fix_loop_placement was already
doing that.  So the following moves this code into fix_loop_placement,
covering both callers now.

	PR tree-optimization/118569
	* cfgloopmanip.cc (fix_loop_placement): When the loops
	nesting parents changed, mark all blocks to be scanned
	for LC PHI uses.
	(fix_bb_placements): Remove code moved into fix_loop_placement.

	* gcc.dg/torture/pr118569.c: New testcase.