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/samd/main.c

@@ -73,23 +73,6 @@ void gc_collect(void) {
     gc_collect_end();
 }
 
-/*
-mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
-    mp_raise_OSError(MP_ENOENT);
-}
-*/
-
-#if !MICROPY_VFS
-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);
-#endif
-
 void nlr_jump_fail(void *val) {
     for (;;) {
     }

ports/samd/mpconfigport.h

@@ -99,15 +99,6 @@
 #define mp_type_fileio mp_type_vfs_lfs1_fileio
 #define mp_type_textio mp_type_vfs_lfs1_textio
 
-// Use VFS's functions for import stat and builtin open
-#define mp_import_stat mp_vfs_import_stat
-#define mp_builtin_open_obj mp_vfs_open_obj
-
-// Hooks to add builtins
-
-#define MICROPY_PORT_BUILTINS \
-    { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&mp_builtin_open_obj) },
-
 #define MICROPY_PORT_ROOT_POINTERS \
     const char *readline_hist[8];