tree-optimization/100329 - avoid reassociating asm goto defs

This avoids reassociating asm goto defs because we have no idea
on which outgoing edge to insert defs.

2021-05-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/100329
	* tree-ssa-reassoc.c (can_reassociate_p): Do not reassociate
	asm goto defs.
	(insert_stmt_after): Assert we're not running into asm goto.

	* gcc.dg/torture/pr100329.c: New testcase.