cpu - Fix order of 8-bit registers in memory

cpu/cpu.h

@@ -66,15 +66,15 @@ struct Cpu_state {
   // Registers
   union {
     u16 BC;
-    struct { u8 B; u8 C; };
+    struct { u8 C; u8 B; };
   };
   union {
     u16 DE;
-    struct { u8 D; u8 E; };
+    struct { u8 E; u8 D; };
   };
   union {
     u16 HL;
-    struct { u8 H; u8 L; };
+    struct { u8 L; u8 H; };
   };
 
   u8 A;