i2c: algos: bit: mention our experience about initial states

So, if somebody wants to re-implement this in the future, we pinpoint to
a problem case.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>