tree-optimization/106112 - fix CSE from wider operation

The following fixes a mistake in looking up an extended operand
in the CSE of a truncated operation.

2022-06-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/106112
	* tree-ssa-sccvn.cc (valueized_wider_op): Properly extend
	a constant operand according to its type.

	* gcc.dg/torture/pr106112.c: New testcase.