Two more patterns for instruction simplifier

This patch allows the instruction simplifier to cover
two more cases:

  x = a + b      and      x = a - b
  y = x - b               y = x + b

In both cases y can be replaced with a, if the types
of arguments are integral.

Change-Id: I4735737f471e31057f1df76ddace5d4d1c79cde6
Test: New tests in 458-checker-instruction-simplification.
Signed-off-by: Max Kazantsev <maxim.kazantsev@intel.com>