Revert "[AMDGPU] Ressociate patterns with sub to use SALU"

The patch will caused dead loop because of DAGCombiner's canonicalization:
  // (x + C) - y  ->  (x - y) + C
  // y - (x + C)  ->  (y - x) - C
  // (x - C) - y  ->  (x - y) - C
  // (C - x) - y  ->  C - (x + y)

This reverts commit b3529b5b.