esp8266/esp_mphal: call_dupterm_read: Use readinto() method.

It's memory fragmentation hazard to allocate 1-char string each time by
calling read() method.

esp8266/esp_mphal.c

@@ -161,16 +161,16 @@ static int call_dupterm_read(void) {
 
     nlr_buf_t nlr;
     if (nlr_push(&nlr) == 0) {
-        mp_obj_t read_m[3];
-        mp_load_method(MP_STATE_PORT(term_obj), MP_QSTR_read, read_m);
-        read_m[2] = MP_OBJ_NEW_SMALL_INT(1);
-        mp_obj_t res = mp_call_method_n_kw(1, 0, read_m);
+        mp_obj_t readinto_m[3];
+        mp_load_method(MP_STATE_PORT(term_obj), MP_QSTR_readinto, readinto_m);
+        readinto_m[2] = MP_STATE_PORT(dupterm_arr_obj);
+        mp_obj_t res = mp_call_method_n_kw(1, 0, readinto_m);
         if (res == mp_const_none) {
             nlr_pop();
             return -2;
         }
         mp_buffer_info_t bufinfo;
-        mp_get_buffer_raise(res, &bufinfo, MP_BUFFER_READ);
+        mp_get_buffer_raise(MP_STATE_PORT(dupterm_arr_obj), &bufinfo, MP_BUFFER_READ);
         if (bufinfo.len == 0) {
             mp_uos_deactivate("dupterm: EOF received, deactivating\n", MP_OBJ_NULL);
             nlr_pop();