opt: add peephole recipe for new normalized boolean

The routine .code.__LEI16 already returns a normalized [0, 1] boolean.

Author: boriel

src/arch/z80/peephole/opts/000_o1_lei16_bool.opt

@@ -0,0 +1,20 @@
+;; core.LEI16 returns the bool result of Byte(a) <= Byte(b)
+;; and is already normalized. The sequence
+;;   sub 1
+;;   sbc a, a
+;;   inc a
+;; can be removed
+
+OLEVEL: 1
+OFLAG: 14
+
+REPLACE {{
+  call .core.__LEI16
+  sub 1
+  sbc a, a
+  inc a
+}}
+
+WITH {{
+  call .core.__LEI16
+}}