exynos: i2c: Tidy up the driver model code

exynos: i2c: Tidy up the driver model code

The existing driver model implementation uses the old non-driver-model code
to operate, but has become impossibly tangled as a result. The actual
algorithm is quite simple.

Also the normal-speed and high-speed buses are quite different and it
doesn't seem that useful to put them in the same driver.

Finally, there is a bug which breaks communication with the Maxim sound
codec and may cause problems with other device.

Rewrite the driver model code for normal-speed operation so that it is
easier to understand, and fix the bug. Add a TODO to split the drivers.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Schocher <hs@denx.de>