windows: Change MICROPY_FLOAT config to new scheme.

windows/mpconfigport.h

@@ -12,7 +12,7 @@
 #define MICROPY_DEBUG_PRINTERS      (1)
 #define MICROPY_ENABLE_REPL_HELPERS (1)
 #define MICROPY_ENABLE_LEXER_UNIX   (1)
-#define MICROPY_ENABLE_FLOAT        (1)
+#define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_DOUBLE)
 #define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_LONGLONG)
 
 // type definitions for the specific machine