gdma_get_free_m2m_trig_id_mask() function

- ESP_OK: Get free M2M trigger IDs successfully - ESP_ERR_INVALID_ARG: Get free M2M trigger IDs failed because of invalid argument - ESP_FAIL: Get free M2M trigger IDs failed because of other error

On some ESP targets (e.g. ESP32C3/S3), DMA trigger used for memory copy can be any of valid peripheral's trigger ID, which can bring conflict if the peripheral is also using the same trigger ID. This function can return the free IDs for memory copy, at the runtime.