py/objdict: Make mp_obj_dict_get_map an inline function.

It's a very simple function and saves code, and improves efficiency, by
being inline.  Note that this is an auxiliary helper function and so
doesn't need mp_check_self -- that's used for functions that can be
accessed directly from Python code (eg from a method table).

py/obj.h

@@ -758,7 +758,9 @@ size_t mp_obj_dict_len(mp_obj_t self_in);
 mp_obj_t mp_obj_dict_get(mp_obj_t self_in, mp_obj_t index);
 mp_obj_t mp_obj_dict_store(mp_obj_t self_in, mp_obj_t key, mp_obj_t value);
 mp_obj_t mp_obj_dict_delete(mp_obj_t self_in, mp_obj_t key);
-mp_map_t *mp_obj_dict_get_map(mp_obj_t self_in);
+static inline mp_map_t *mp_obj_dict_get_map(mp_obj_t dict) {
+    return &((mp_obj_dict_t*)MP_OBJ_TO_PTR(dict))->map;
+}
 
 // set
 void mp_obj_set_store(mp_obj_t self_in, mp_obj_t item);

py/objdict.c

@@ -600,9 +600,3 @@ mp_obj_t mp_obj_dict_delete(mp_obj_t self_in, mp_obj_t key) {
     dict_get_helper(2, args, MP_MAP_LOOKUP_REMOVE_IF_FOUND);
     return self_in;
 }
-
-mp_map_t *mp_obj_dict_get_map(mp_obj_t self_in) {
-    mp_check_self(MP_OBJ_IS_DICT_TYPE(self_in));
-    mp_obj_dict_t *self = MP_OBJ_TO_PTR(self_in);
-    return &self->map;
-}