ig4: Fix FIFO depths detection

At least on my Tiger Lake-LP queue depth detection failed before the
ig4iic_set_config() call, resulting in no FIFO use. Moving it after
solves the problem, getting proper 64 bytes size.

On my Dell XPS 13 9310 with iichid(4) touchscreen and touchpad this
by few times reduces context switch rate in the driver, and probably
also improves the I2C bus utilization.

MFC after: 1 month