Reported as PR 93321, prepare_block_for_update with some huge
recusive inlining can go past the stack limit. Transforming this
recursive into worklist improves the stack usage here and we no
longer seg fault for the testcase.  Note the order we walk the siblings
change.

ChangeLog:
	PR tree-opt/93321
	* tree-into-ssa.c (prepare_block_for_update_1): Split out from ...
	(prepare_block_for_update): This.  Use a worklist instead of recursing.