with the i2c bus operating at 400kHz this achieves a 4.8kHz SPI clock
rate which could be worse.
It accepts the same style of init sequence as displayio.
tested by scoping the pins on the espressif lcd dev kit with a dummy init sequence:
```python
dotclockframebuffer.ioexpander_send_init_sequence(
bus=bus,
i2c_address=expander_addr,
gpio_address=1,
gpio_data_len=1,
gpio_data=0xff,
cs_bit=1,
mosi_bit=3,
clk_bit=2,
init_sequence=init_sequence)
```
Jeff Epler