
iic_acquire_bus() / iic_release_bus(). "acquire" and "release" hooks no longer need to be provided by back-end controller drivers (only if they need special handling, e.g. powering on the i2c controller). This results in the removal of a bunch of rendundant code from each back-end controller driver. Assert that we are not in hard interrupt context in iic_acquire_bus(), iic_exec(), and iic_release_bus().