ports: Use default VFS config for import_stat and builtin_open.

For ports with MICROPY_VFS and MICROPY_PY_IO enabled their configuration
can now be simplified to use the defaults for mp_import_stat and
mp_builtin_open.

This commit makes no functional change, except for the following minor
points:
- the built-in "open" is removed from the minimal port (it previously did
  nothing)
- the duplicate built-in "input" is removed from the esp32 port
- qemu-arm now delegates to VFS import/open

Signed-off-by: Damien George <damien@micropython.org>

ports/qemu-arm/main.c

@@ -45,15 +45,6 @@ mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
     mp_raise_OSError(MP_ENOENT);
 }
 
-mp_import_stat_t mp_import_stat(const char *path) {
-    return MP_IMPORT_STAT_NO_EXIST;
-}
-
-mp_obj_t mp_builtin_open(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_KW(mp_builtin_open_obj, 1, mp_builtin_open);
-
 void nlr_jump_fail(void *val) {
     printf("uncaught NLR\n");
     exit(1);

ports/qemu-arm/mpconfigport.h

@@ -61,10 +61,6 @@ typedef int32_t mp_int_t; // must be pointer size
 typedef uint32_t mp_uint_t; // must be pointer size
 typedef long mp_off_t;
 
-// extra built in names to add to the global namespace
-#define MICROPY_PORT_BUILTINS \
-    { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&mp_builtin_open_obj) },
-
 // We need to provide a declaration/definition of alloca()
 #include <alloca.h>
 

ports/qemu-arm/test_main.c

@@ -5,7 +5,6 @@
 #include <malloc.h>
 #include <setjmp.h>
 
-#include "py/builtin.h"
 #include "py/compile.h"
 #include "py/runtime.h"
 #include "py/stackctrl.h"
@@ -39,15 +38,6 @@ mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
     mp_raise_OSError(MP_ENOENT);
 }
 
-mp_import_stat_t mp_import_stat(const char *path) {
-    return MP_IMPORT_STAT_NO_EXIST;
-}
-
-mp_obj_t mp_builtin_open(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_KW(mp_builtin_open_obj, 1, mp_builtin_open);
-
 void nlr_jump_fail(void *val) {
     printf("uncaught NLR\n");
     exit(1);