Revert "remove demorgan rules (bytecodealliance#12127)"

This reverts commit 39f8c4e.

Author: bongjunj

cranelift/codegen/src/opts/bitops.isle

@@ -41,6 +41,14 @@
 ;; not(not(x)) == x.
 (rule (simplify (bnot ty (bnot ty x))) (subsume x))
 
+;; DeMorgan's rule (two versions):
+;; bnot(bor(x, y)) == band(bnot(x), bnot(y))
+(rule (simplify (bnot ty (bor ty x y)))
+      (band ty (bnot ty x) (bnot ty y)))
+;; bnot(band(x, y)) == bor(bnot(x), bnot(y))
+(rule (simplify (bnot ty (band t x y)))
+      (bor ty (bnot ty x) (bnot ty y)))
+
 ;; `or(and(x, y), not(y)) == or(x, not(y))`
 (rule (simplify (bor ty
                      (band ty x y)