middle-end/98773 - always sign extend CHREC_RIGHT

middle-end/98773 - always sign extend CHREC_RIGHT

The previous change exposed a miscompile when trying to interpret
CHREC_RIGHT correctly which in fact it already was to the extent
it is used.  The following reverts this part of the change, only
retaining the singling out of HOST_WIDE_INT_MIN.

2021-01-22  Richard Biener  <rguenther@suse.de>

	PR middle-end/98773
	* tree-data-ref.c (initalize_matrix_A): Revert previous
	change, retaining failing on HOST_WIDE_INT_MIN CHREC_RIGHT.

	* gcc.dg/torture/pr98773.c: New testcase.