py: Introduce MP_ROM_FALSE/MP_ROM_TRUE for ROM to refer to bool objects.

This helps to prevent mistakes, and allows easily changing the ROM value of
False/True if needed.

extmod/vfs.c

@@ -201,8 +201,8 @@ STATIC mp_obj_t mp_vfs_autodetect(mp_obj_t bdev_obj) {
 mp_obj_t mp_vfs_mount(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_readonly, ARG_mkfs };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_readonly, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_false_obj)} },
-        { MP_QSTR_mkfs, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_false_obj)} },
+        { MP_QSTR_readonly, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_FALSE} },
+        { MP_QSTR_mkfs, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_FALSE} },
     };
 
     // parse args

ports/esp32/modesp32.c

@@ -158,8 +158,8 @@ STATIC const mp_rom_map_elem_t esp32_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_RMT), MP_ROM_PTR(&esp32_rmt_type) },
     { MP_ROM_QSTR(MP_QSTR_ULP), MP_ROM_PTR(&esp32_ulp_type) },
 
-    { MP_ROM_QSTR(MP_QSTR_WAKEUP_ALL_LOW), MP_ROM_PTR(&mp_const_false_obj) },
-    { MP_ROM_QSTR(MP_QSTR_WAKEUP_ANY_HIGH), MP_ROM_PTR(&mp_const_true_obj) },
+    { MP_ROM_QSTR(MP_QSTR_WAKEUP_ALL_LOW), MP_ROM_FALSE },
+    { MP_ROM_QSTR(MP_QSTR_WAKEUP_ANY_HIGH), MP_ROM_TRUE },
 };
 
 STATIC MP_DEFINE_CONST_DICT(esp32_module_globals, esp32_module_globals_table);

py/obj.h

@@ -246,6 +246,11 @@ typedef union _mp_rom_obj_t { uint64_t u64; struct { const void *lo, *hi; } u32;
 #define MP_ROM_NONE MP_ROM_PTR(&mp_const_none_obj)
 #endif
 
+#ifndef MP_ROM_FALSE
+#define MP_ROM_FALSE MP_ROM_PTR(&mp_const_false_obj)
+#define MP_ROM_TRUE MP_ROM_PTR(&mp_const_true_obj)
+#endif
+
 #ifndef MP_ROM_INT
 typedef mp_const_obj_t mp_rom_obj_t;
 #define MP_ROM_INT(i) MP_OBJ_NEW_SMALL_INT(i)