lib/utils: Change default value of pyexec_mode_kind to 0 to put in bss.

By simply reordering the enums for pyexec_mode_kind_t it eliminates a data
variable which costs ROM to initialise it.  And the minimal build now has
nothing in the data section.

It seems the compiler is smart enough so that the generated code for
if-logic which tests these enum values is unchanged.

lib/utils/pyexec.h

@@ -29,8 +29,8 @@
 #include "py/obj.h"
 
 typedef enum {
-    PYEXEC_MODE_RAW_REPL,
     PYEXEC_MODE_FRIENDLY_REPL,
+    PYEXEC_MODE_RAW_REPL,
 } pyexec_mode_kind_t;
 
 extern pyexec_mode_kind_t pyexec_mode_kind;